Misc. imorvements as discussed in RW/KB worksho

* preparation for a context menu to send text messages from ATC/aircraft view
* preparation for context menu for fast pos. updates
* reverse ICAO lookup at login screen
* display fast updates / parts in GUI
* moved max- aircraft into settings
* made serverselection own component

src/blackgui/components/atcstationcomponent.h

@@ -52,6 +52,10 @@ namespace BlackGui
             //! Number of online stations
             int countOnlineStations() const;
 
+        signals:
+            //! Request a text message
+            void requestTextMessage(const BlackMisc::Aviation::CCallsign &callsign);
+
         public slots:
             //! Update stations
             void update();