refs #382, reviewed audio context handling

* only init QDbusServer for P2P
* changed init order of contexts in runtime
* use "fake" signal to call setComVoiceRooms (remote in GUI)
* added slot to change voice room callsign
* used "org.swift" instead of "net.vatim" (just style)
* used const QString for serviceName
* added correct copyright header (just style)

src/blackcore/context_audio_proxy.cpp

@@ -130,6 +130,14 @@ namespace BlackCore
         this->m_dBusInterface->callDBus(QLatin1Literal("setComVoiceRooms"), voiceRooms);
     }
 
+    /*
+     * Own voice room callsign
+     */
+    void CContextAudioProxy::setOwnCallsignForRooms(const CCallsign &callsign)
+    {
+        this->m_dBusInterface->callDBus(QLatin1Literal("setOwnCallsignForRooms"), callsign);
+    }
+
     /*
      * Play SELCAL tone
      */