Revert "Revert "Bug 717062 - Root preferences branch for simple-prefs needs to be configurable r=@erikvold""

This reverts commit 3784678ed07b074295bacd7d67ca259b043c0b8c.
Bug 717062 exposing require("sdk/self").preferencesBranch
Bug 936623 - Deprecate Widget
Bug 847593 - Remove tab-browser
Stop creating loaders than are never unloaded.
Merge pull request #1329 from Gozala/bug/test-runner@787390

Bug 787390 - Stop creating loaders than are never unloaded. r=@jsantell
Implement toolbar API.
Merge pull request #1307 from Gozala/bug/toolbar@787390

Bug 787390 - Toolbar & Frame API implementations. r=@ZER0
Merge pull request #1328 from erikvold/847593

Bug 847593 - Remove tab-browser r=@gozala
Bug 951317 - Split Button API in ActionButton and ToggleButton
Merge pull request #1327 from ZER0/button/951317

fix Bug 951317 - Split Button API in ActionButton and ToggleButton r=@gozala
Fix regression from #1327 r=@jsantell
Hotfix regression introduced by #1299 a=@gozala
Bug 913559: Use parent loader's console when another isn't provided.
Filter out deprecation messages from tabs tests.
Bug 946813 - Part 2: Expose invisibleToDebugger via the loader. r=jsantell
Merge pull request #1332 from jryans/loader-itd

Bug 946813 - Part 2: Expose invisibleToDebugger via the loader. r=@jsantell
Bug 903002 - Display properly the widget with panel attached, in Australis
Merge pull request #1172 from ZER0/australis-widget/903002

Bug 903002 - Display properly the widget with panel attached, in Australis r=@gozala
Bug 926727 Detraitify worker