Revise data limit notifs, watch kernel alerts.

Teach NetworkPolicy limits to "snooze" when requested by user, and
notify with both dialog and notification.  Register for network alerts
through NMS to trigger updates immediately instead of waiting for
next stats update.

Enforce that all NetworkPolicy are unique on a template basis, and
move SCREEN_ON/OFF broadcasts to background thread.  Launch SystemUI
and Settings directly instead of using actions, and include full
NetworkTemplate in extras.

Tests to verify notification and snooze behavior.

Bug: 5057979, 5023579, 4723336, 5045721
Change-Id: I03724beff94a7c0547cb5220431ba8d4cd44d077