Bug 984503 - Part 1: Add menu option to remove Firefox Account.
Bug 984503 - Part 2: Add "More..." to Firefox Account status list.
Bug 984503 - Part 3: Hide "More..." option if device has a hardware menu button.

The reason for this dance is to keep the "Remove Account" button out of
view if at all possible.  I don't want to make it too easy to delete
your account.
Bug 984503 - Part 4: Show a toast after removing Firefox Account.
Bug 984503 - Add "Remove Firefox Account" menu option to FxAccount status activity. r=nalexander,rnewman

The menu is exposed as "More..." on devices that do not have a hardware
menu button.