tweak color of quadruped robot URDF, tweak quadruped.py script to make it more compatible with VR demo

allow VR physics server to run with or without 'realTimeSimulation'

examples/SharedMemory/PhysicsServerCommandProcessor.h

@@ -85,6 +85,7 @@ public:
 	void replayFromLogFile(const char* fileName);
 	void replayLogCommand(char* bufferServerToClient, int bufferSizeInBytes );
 	void stepSimulationRealTime(double dtInSec);
+	void enableRealTimeSimulation(bool enableRealTimeSim);
 	void applyJointDamping(int bodyUniqueId);
 };