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
I do not challenge the steps itself, I'm asking whether the steps are needed after this PR get integrated? At least some required packages need to be added in the .spec file.