Add preliminary PhysX 4.0 backend for PyBullet

Add inverse dynamics / mass matrix code from DeepMimic, thanks to Xue Bin (Jason) Peng
Add example how to use stable PD control for humanoid with spherical joints (see humanoidMotionCapture.py)
Fix related to TinyRenderer object transforms not updating when using collision filtering

src/BulletDynamics/Featherstone/btMultiBody.h

@@ -182,7 +182,10 @@ public:
 	// get/set pos/vel/rot/omega for the base link
 	//
 
-	const btVector3 &getBasePos() const { return m_basePos; }  // in world frame
+	const btVector3 &getBasePos() const 
+	{ 
+		return m_basePos; 
+	}  // in world frame
 	const btVector3 getBaseVel() const
 	{
 		return btVector3(m_realBuf[3], m_realBuf[4], m_realBuf[5]);