W3C Telephony API implementation.

Implements the latest W3C Telephony API specification found at http://telephony.sysapps.org/
Requires the oFono telephony middleware and the BlueZ Bluetooth middleware for working with paired phones.

BUG=XWALK-1419
These are not needed for building or running the extension.
They are needed as helpers for testing. Two different things. It would be an error including them in the spec file.