Support for Telecom Call IDs.

Add support for caching telecom call ID in connection and conference
classes.

Enhance connection service call ID generation:
For "existing calls", the connection service will try to use a call ID
of the format ClassName@ID
Where ClassName is the ComponentName of the connection service, and ID
is a unique incrementing ID for the connection service.

Bug: 23357902
Change-Id: I2284b018465e2b330fc8a3b556758e9f34a2daba