0.7:
* Fix bugs that unexpected texts are displayed in group view mode
* Fix bugs that columns are not displayed in the search dialog
* Clean up code

0.6:
* Fix the bug that the column handler is not added
* Support version 13 and later
* Change code to use addEventListener intead of the "oncommand" attribute to prevent vulnerabilities
* Remove code using RDF, dropping support of version 2.0 or before
* Fix a string to avoid a validator bug

Support new versions up to 5.*

Fix the bug that overlays of other add-ons do not work