pybullet vr_kuka_setup.py: add a gear joint, to keep the gripper centered,

vr_kuka_control.py: control all joints, use analogue button to close gripper
remove some debug warnings/prints
pybullet, avoid crash in changeUserConstraint if not passing a [list]
allow some gym environments (pybullet_pendulum and locomotors) to re-use an existing physics client connection.

examples/SharedMemory/PhysicsDirect.cpp

@@ -903,7 +903,7 @@ void PhysicsDirect::postProcessStatus(const struct SharedMemoryStatus& serverCmd
 	}
 	case CMD_CHANGE_USER_CONSTRAINT_FAILED:
 	{
-		b3Warning("changeConstraint failed");
+		//b3Warning("changeConstraint failed");
 		break;
 	}