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/PhysicsServerSharedMemory.h

@@ -28,6 +28,8 @@ public:
 
 	virtual void stepSimulationRealTime(double dtInSec);
 
+	virtual void enableRealTimeSimulation(bool enableRealTimeSim);
+
 	//bool	supportsJointMotor(class btMultiBody* body, int linkIndex);