Use AtomicFile for usermanager files.
Added a MANAGE_USERS permission that apps (signature permission) can use
to create/query/modify/remove users.
Change-Id: I5cf232232d0539e7508df8ec9b216e29c2351cd9
Moved a bunch of methods from PackageManager to UserManager.
Fix launching of activities from recents to correct user.
Guest creation APIs
Change-Id: I0733405e6eb2829675665e225c759d6baa2b708f