Refactor CContextSimulator::loadSimulatorPlugin

When a plugin is loaded, existing aircrafts should not be added
immediatly, but as soon as the simulator is simulating.
CContextSimulator also handles now the case that no simulator is
attached and all aircraft slots are now doing nothing instead of
raising an assert.

refs #549

src/blackcore/context/contextsimulator.h

@@ -183,6 +183,9 @@ namespace BlackCore
             //! Simulator avialable (driver available)?
             bool isSimulatorAvailable() const { return BlackConfig::CBuildConfig::isCompiledWithFlightSimulatorSupport() && !getSimulatorPluginInfo().isUnspecified(); }
 
+            //! Is available simulator simulating? Returns false if no simulator is available
+            bool isSimulatorSimulating() const;
+
             //! Icon representing the model
             virtual BlackMisc::CPixmap iconForModel(const QString &modelString) const = 0;