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 there to help testing, and in general everyone who is going to use this code. If I remove it, where to put? I assume it's better if doc comes with the code.