Apply restrictions right away instead of on exit

Use usermanager to clear restrictions, as it needs to do a bunch of
book keeping.

Apply PIN restriction to master clear button.

Changing existing PIN now includes verifying the PIN, so it doesn't
need to be cleared here in Settings.

Removed automatic persisting of restrictions on receiving them unless
it is a restricted profile.

Make apps that are signed with platform certs immutable and ON.

Change-Id: Iffd1bf2eb0d18202fb66ddcf80668baa8e6b84ed