fx22: fix no icons in opened tab list

* https://bugzilla.mozilla.org/show_bug.cgi?id=828508
* https://bugzilla.mozilla.org/show_bug.cgi?id=860578
change keys to open panel in URL bar

* change a modifier key from 'Ctrl' to 'Alt'
* fix an unexpected popup when selecting a part of URL
fix missing quotation mark
update comments
re-change keys to open panel in URL bar

* improve commit: e5adb31
* change modifier keys from 'Alt' to 'Ctrl+Alt' to avoid toggling the menu bar