Eloi Bail authored Feb 20, 2015 and Guillaume Roguez committed Feb 24, 2015

Refs #66623

**WARNING**

This commit modify DBUS API.
API are modified only for libringclient.
Gnome client - not based on libringclient - will be unstable.

Change-Id: Ib7ddd32327f3ccb9fccc6c65a0fc93d7defd76f5