Some fixes / tweaks / Doxygen:

* helper method to detect disconnected state
* clear ATC info if disconnected or not available
* unit test for "finders"
* added Doxygen file
* formatting frequency in text message tabs

src/blackgui/atcstationcomponent.h

@@ -72,6 +72,9 @@ namespace BlackGui
         //! Online stations changed
         void changedAtcStationsOnline();
 
+        //! Connection status has been changed
+        void connectionStatusChanged(uint from, uint to, const QString &message);
+
     private:
         Ui::CAtcStationComponent *ui;
         CTimerBasedComponent *m_timerComponent;