Bug 559306: Allowing chrome.manifest file, and chrome folder for jetpacks

(cherry picked from commit 4922f171502f91a6ac14d5f5a67264d35c84b625)
Merge pull request #976 from jsantell/favicon

Bug 861955 getFavicon async method in io/data, r+=@erikvold
Merge pull request #964 from erikvold/559306

Bug 559306: Allow adding a chrome.manifest file and chrome folder r=@gozala r=@ochameau
Move getFavicon method
Bug 834942, deprecate tab favicon getter, repurpose getFavicon