Add "Clear Downloads" menu item to panel context menu
(draft for #8)
Use strings from Firefox localization for "Clear Downloads" menu item
(#8)
Add special context menu for download panel footer
(#8)
Check for Services.downloads.canCleanUp/canCleanUpPrivate
(#8)
Add ability to correct acceskey for "Clear Downloads"
(also needed in Firefox < 20)
(#8)
Don't use "global" command event for "Clear Downloads" action
(#8)
Correctly ignore missing DownloadsSummaryData.prototype._updateView()
(at least for Firefox 17)
Correctly get download panel footer in Firefox < 20
Correct margins for file icon and description (only in Library)
(related to #7)