Fixed a bug that prevented Send Later from running in recent Thunderbird Beta releases

Send Later version 9 contains many internal changes from the 8.x branch, but relatively few user-facing changes.

Added features:
* Restore original schedule when editing an existing message.
* Enable customizing they format in which dates & times are displayed.

General improvements:
* A lot of application-specific code has been moved into the sandboxed background context
* Several specialized experiment functions have been replaced with official webextension api's
- e.g. notifications are now created using HTML windows rather than native popups
* Other extensions can now modify the message or cancel sending as they would when the message is being sent normally

Set maximum Thunderbird version for Send Later 8.9. Will be moving to 9.0 with next Thunderbird ESR.

Bug fix: format internal dates with "Sep" rather than "Sept" for compliance with standards. This fixes issues with pedantic mail servers that reject improperly formatted dates.

Fix for compatibility with Thunderbird 91

Revert changes from the previous release that were causing problems for some users.

Added features:

* "accelerator" keys can be used to alter the behavior of the composeAction toolbar button. If you hold Shift or Ctrl (cmd on MacOS) while clicking the "Send Later" toolbar button, then special functions will be executed rather than opening the scheduler dialog. These behaviors can be configured in the options dialog in the same way you configure shortcut keys.

Bug fixes:

* The status bar menu should always respect changes to the "Show Send Later in status bar" preference.
* Sorting draft messages by the "Send Later" column should work as expected now. The draft folder column should be generally much less finicky than it was before.

Notes:

Lots changed under the hood in this release, primarily around the way UI components are handled. Features like the drafts folder column and the status bar menu should be more reliable than they were before. However, if you notice any irregularities with the way those elements are behaving please do let me know.

Several minor bug fixes and incremental improvements.

Updated translations

Bug fix: Use proper translations for relative time strings.

* Update/improve lots of translation strings
* Make relative time display more specific (e.g. "2.7 hours from now" rather than rounding down to "2 hours from now")
* Several minor bug fixes

Fixed translations for users with unsupported regional locale variants

Updated translations for most supported languages
Several minor bug fixes

Lots of minor tweaks and behind the scenes code improvements since version 8.5. Some highlights include:

* Lots of improvements to the scheduler interface that should cover most edge cases, and generally improve usability of the scheduling popup.
* Implement a number of alerts to help prevent user from performing unintended actions (notify on quit, when editing a previously scheduled message, when using 'send now' and 'place in outbox', etc).
* Handle how late grace period and scheduling restrictions in a more graceful/intuitive way.
* Improve ability to identify non-standard drafts folders.

For a complete list of all changes since the previous version, see the release notes on Send Later's github page: https://github.com/Extended-Thunder/send-later/releases/

Fixes bug with locating the draft folder message enumerator for local drafts folder.

Changes since 8.4.5:

Features:

* Status bar menu/indicator is back
* Access key shortcuts are available within the message composition window and the popup dialog
* In the composition window, Ctrl+Alt+1/Ctrl+Alt+2/Ctrl+Alt+3 execute the user-defined shortcuts (15 min/30 min/ 2 hour delay by default)
* In the popup dialog Ctrl+1/Ctrl+2/Ctrl+3 also execute the shortcuts, Ctrl+Enter activates the "Send at ..." button, the "Send Now" and "Place in Outbox" buttons are connected to the same access keys as they were in the 7.x branch, with underlined characters in the button text to indicate what those keys are, and the shortcut keys can be manually bound to whatever arbitrary access key you'd like by placing an & character in the shortcut label immediately preceding the character of your choice.
- e.g. creating a shortcut called Next &Work Day would be rendered in the shortcut button as Next Work Day (W should be underlined, but github won't do that), and could be activated with Alt+Shift+W on Windows and Linux, or Ctrl+Option+W on Mac.
* Automatically re-save drafts when they are opened for editing, effectively "un-scheduling" them.
* Send rate throttling is possible, via an advanced configuration setting
* Indicate in drafts folder column when a draft is invalid due to pgp encryption, or is not scheduled by this specific instance of Thunderbird.

Bug fixes and performance enhancements:

* Fetch messages from the server only as absolutely necessary.
* More judicious console log handling
* Date/time locales are fixed for users whose default locale was different than their UI locale
* Ensure overlay scripts are injected in the correct order every time
* Fix the state lock for messages during 'place in outbox' operation (to avoid infinite spell check loop)
* Minor fixups and improvements to the options page interface
* Fix cases where an account has no dedicated "drafts" folder, by also checking the "templates" folder for scheduled drafts.

This patch implements a workaround for Send Later's most serious bug report: cases in which send later was not correctly processing messages at their scheduled time.

It also includes lots of tweaks to keep Send Later running smoothly, including:

* Minor improvements and fixups to the scheduler dialog.
- Option to place message in outbox rather than send immediately
- Automatically adjust input based on schedule restrictions
- Relative time format is synchronized with the actual time at which send later executes (not necessarily on the minute)
- Relative time text updates periodically while the dialog remains open, rather than only being set when the input fields change.
- Fix bug with "save these values as defaults" in which default values were not properly restored.
* Fix locales, and merge translation changes from the 7.x branch
* Implement all the same pre-send checks as Thunderbird's native send operation, and make sure they only run once.
* Handle errors in cases where saveAsDraft fails to complete.
* Delay automatic updates until next restart (will not take effect until an update is available via ATN after this version)
* Offer opt-out from repeated resent message warnings

This update improves reliability of the overlay components like the draft folder column and the compose window button. It also fixes a number of edge-case bugs related to user scheduling functions, and optimizes several behind the scenes functions. Most users will not notice much difference from version 8.1, but things should run more smoothly over all.

As always, please contact me via email or through GitHub if you are experiencing issues with Send Later.

This is a very minor patch that forces Thunderbird to include the Send Later button in composition windows. This should happen automatically, but in some cases it was not happening for whatever reason.

We are pleased to announce that Send Later will remain compatible with Thunderbird throughout the ongoing transition to the WebExtension framework.

This version represents a major rewrite of the Send Later code base, and therefore some features have changed slightly, and a handful of minor features have yet to be carried over from the 7.x branch. That said, the new version should feel familiar to long time Send Later users, and incorporates all of the core functionality.

The new code base has been available in beta since August, and has been downloaded by about a thousand users. We have addressed all significant bugs reported by those beta testers, but we are aware that there are always speed bumps with major overhauls like this one. We encourage you to submit bug reports via the project's GitHub page if you find anything not working as expected.

Somehow some Dutch strings ended up in the Danish translation. I have no idea how this happened, but it's fixed now.

Remove Kickstarter campaign pop-up, since the campaign has succeeded and is almost over.

Fix bug in putting previous scheduled send time in compose toolbar

If the user adds the send time text box to the compose toolbar and then edits a previously scheduled message, the previous send time is supposed to show up in the text box automatically, but instead the word "long" was showing up because I forgot a couple of curly braces in a date formatting string. I'm amazed that this has been broken for almost six months and no one has mentioned it to me before now.

Translation updates

Complete Catalan, Chinese (both simplified and traditional), Finnish, Galician, Portuguese (both European and Brazilian), and Russian translations.

Add to (not yet finished) Danish, Polish, and Slovenian translations.

As always, thank you to my translators!

Fix bug in putting previous scheduled send time in compose toolbar

If the user adds the send time text box to the compose toolbar and then edits a previously scheduled message, the previous send time is supposed to show up in the text box automatically, but instead the word "long" was showing up because I forgot a couple of curly braces in a date formatting string. I'm amazed that this has been broken for almost six months and no one has mentioned it to me before now.

Translation updates.

Compatibility fixes for Thunderbird 45 and Thunderbird 52.

Translation updates.

Add the Kickstarter campaign pop-up to the Thunderbird 60 version of Send Later.

Translation update

This add-on will no longer be supported when Thunderbird 78 is released in a few months, unless enough people commit to supporting continued maintenance of the add-on to make it feasible. To show your commitment, please visit https://www.kickstarter.com/projects/jik/rewritten-add-ons-for-mozilla-thunderbirds-next-release and make a pledge. As a bonus, Kickstarter supporters of this and my other add-ons will receive significant discounts on add-on licenses.

This release of the add-on adds a pop-up message warning users about the potential end of support and encouraging people to visit the Kickstarter campaign and support it.

Fix errors for users of Thunderbird in Danish.