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
`*` and `&` need followed by type, `GVariantIter *props` > `GVariantIter* props`, please ally this rule in general