EmergencyNumber enhancement

Patch set 1-2:
1) Add Database source for EmergencyNumber
2) add mergeEmergencyNumber for merging two emergency numbers

Patch set 3-5:
3) enable Listener.EmergencyNumber enhancement

Patch set 6:
4) no need to pass any parameter to PhoneNotifier
5) modify API documentation

Patch set 9:
6) deprecate PhoneNumberUtils.isEmergencyNumber
7) modify API documentation for security exception and backward
compatibility
9) introduce some utils in EmergencyNumber for merging number purposes

Patch set 12:
10) add mnc into EmergencyNumber

Bug: 112657134
Test: Treehugger
Change-Id: I0dcd01bdad7d9c37294cd8b87eda54b4ac9d0a0b