Implementation of Remote-SIM.

Design doc http://shortn/_GG690j15js

Added the following changes to SubscriptionController
1. Update Cached Subscriptions to include Remote-SIM subscriptions
2. Addition/Removal of a Remote-SIM subscription
3. Changes to the code updating defaults (fallback, voice, sms, data)
   to take Remote-SIM subscriptions into account.
4. Change internal datastruct to allow multiple SIMs in a single
   slotindex. Currently, only Remote-SIMs are inserted into
   the same slotindex.

Bug: 112321331
Test: tested w/ unittests

Change-Id: I2553a8f2e74419a13721e236a7f22e3c746429f7