SITL: add multi-vehicle support to rcS

This also removes the HIGHRES_IMU mavlink stream to the GCS. I don't see
why it's needed and it adds noticeable CPU load.

src/modules/simulator/simulator.cpp

@@ -142,7 +142,7 @@ void Simulator::parameters_update(bool force)
 int Simulator::start(int argc, char *argv[])
 {
 	int ret = 0;
-	int udp_port = 0;
+	int udp_port = 14560;
 	_instance = new Simulator();
 
 	if (_instance) {