Bug 962299 - Pre: add getByteArray methods to ExtendedJSONObject.
Bug 962299 - Part 1: add profile field to FxAccount.
Bug 962299 - Part 2: first stab at using a single JSON blob for user data.
Review comment: handle number format exceptions.
Review comment: updateBundleDataBytes.
Review comment: note about profile deletion.
Bug 962299 - Bundle account data into a single userdata field and add profile tracking. r=nalexander