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
Merge branch 'master' of github.com:zolkis/tizen-extensions-crosswalk into telephony
Fixed review comments