Bug 906884 - Set Fennec ContentProvider android:label meta-data for next-gen Sync. r=rnewman

These titles show up in the list of things to Sync in Android Settings
> Accounts and Sync > [account].
Bug 808813 - Part 1: Add MOZ_ANDROID_SHARED_FXACCOUNT_TYPE. r=rnewman
Bug 808813 - Part 2: Implement Firefox Account Android account type. r=rnewman
Bug 808813 - Part 3: Add FxAccount manifest declarations. r=rnewman