Group own aircraft DBus calls together

Previously all own aircraft values were request via single DBus calls.
Since DBus allows up to 8 values in its reply, use this mechanism
to group the requests and reduce the amount of single calls.

src/plugins/simulator/xplane/xswiftbusserviceproxy.h

@@ -34,6 +34,8 @@ namespace BlackSimPlugin
 {
     namespace XPlane
     {
+        struct XPlaneData;
+
         /*!
          * Proxy object connected to a real XSwiftBus::CService object via DBus
          */
@@ -94,6 +96,9 @@ namespace BlackSimPlugin
             void airportsInRangeUpdated(const QStringList &icaoCodes, const QStringList &names, const QList<double> &lats, const QList<double> &lons, const QList<double> &alts);
 
         public slots:
+            //! Get own aircraft situation data
+            void getOwnAircraftSituationData(XPlaneData *o_xplaneData);
+
             //! \copydoc XSwiftBus::CService::addTextMessage
             void addTextMessage(const QString &text, double red, double green, double blue);