Fix for FF5.0

Fixes small conflict with Addons Manager Hilite.

Performance improvements for 6.0.
Addon ID is now in a tooltip for the versions label.
Fixed preferences window title.

Updated to work with FF4.0 and TB3.3.

Compatibility is still displayed in the newer versions, but due to changes in the new Addons programming interfaces, checking for compatibility updates has been removed.

This is a minor update that adds Thunderbird 3.0 and 3.1 to the compatibility list (user requested), and bumping the Firefox compatibility max version down to 3.6.* from 3.7a1pre, since FF3.7 has been promoted to 4.0.

This addon does NOT work with Thunderbird 3.3 or Firefox 4.0, since they completely redid the addons manager for these versions. I might look into updating the addon for these, but I make no guarantees.

Minor update, fixed faulty event detection.