Add SMS Middleware layer.

Add fix so ordered broadcasts are delivered to system
apps first in the event of a tie. This works around
the issue where terrible apps steal SMS notifications
from the broadcast queue to simply prevent notifications
that could otherwise be removed by a toggle.

PatchSet: rebase + string correction

Change-Id: I4fff0c584f8fce9c5f2f4fe86a82fe6480c307c7