Fixed mute handling and audio LED

* AFV client has own "changedMute" signal
* unmute if started/stopped AFC client
* in statusbar also check audio start/stop to refresh LEDs
* see https://discordapp.com/channels/539048679160676382/539486309882789888/713491666971000872

src/blackcore/afv/clients/afvclient.h

@@ -313,6 +313,9 @@ namespace BlackCore
                 //! Audio has been stopped
                 void stoppedAudio();
 
+                //! Mute changed
+                void changedMute(bool muted);
+
             protected:
                 //! \copydoc BlackMisc::CContinuousWorker::initialize
                 virtual void initialize() override;