External mutation of full NetworkPolicy set.

Instead of embedding complex template coexistence rules into policy
service, rely on external editors to enforce, and offer atomic
get/set operations for full policy sets.

Generate default mobile policy when none exists, using default of 4GB
warning and cycle reset of current day.  Dispatch listener events
through Handler when holding internal lock, and catch CLASS_UNKNOWN
networks in 3G_LOWER template.

Change-Id: I063cf1eaf330e32b75d0697b89fc04488e6dfaea