Improvement to the FF extension's context menu

Specifically:
 - Bug 1068342 - Add a "Reload in Adobe Flash Player" context menu item to fallback back from Shumway to Flash (we had this under a different name)
 - Bug 1064435 - Add "About Shumway [version]" context menu item, like Flash plugin's "About Adobe Flash Player [version]" (without the [version] part for now, because that's a bit annoying to do/hard to make work without introducing startup time regressions)
 - Bug 1064005 - Shumway "Report Problems" context menu item does nothing: ReferenceError: avm2 is not defined viewer.js:171
 - No Bug - change the "Report Problems" entry to open a bugzilla.mozilla.org bug entry form prefilled with some useful information and set to the correct component
Merge pull request #1723 from tschneidereit/master

Improvement to the FF extension's context menu