Telephony cleanup

This CL removes the PSTN and SIP call service providers.
The connection services will now be looked up by package
manager instead.

This CL also cleanups the telephony connection service code.
Now that the SIP code has been moved out the code can be much
simpler and PstnConnection* and TelephonyConnection* can be
merged.

Change-Id: I2e40c5c64c0d242dc41b680943d7e9209142db5b
16 files changed