Telephony: Implementation of DATA+MMS.

- Initial implementation of Msim data.
- Implemented DDS switch and auto-retrieval.
- Implemented plugin for DDS switch service.
- Serialize on-demand DDS switch logic.
- Implement callback interface between DCT and SubscriptionController
for onDemandDds requests

Change-Id: If69fc8b4f90bfb07c66c6520a4586e510166767b
Conflicts:
src/java/com/android/internal/telephony/dataconnection/DcTracker.java