Fix intent filter priorities

There are now three rules that guard intent filter priorities:
1) Only privileged applications will be granted a >0 priority
   filter [previously, _all_ system applications could do this]
2) There are certain actions that are considered protected [eg
   ACTION_VIEW, ACTION_SEND, ...] and even privileged applications
   will NOT be granted a >0 priority filter. There is one, and
   only one, exception for the SetupWizard.
3) Updates will NOT be granted a priority greater than the priority
   defined on the system image.

Bug: 27450489
Change-Id: Ifcec4d7a59e684331399abc41eea1bd6876155a4