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

examples/SharedMemory/physx/URDF2PhysX.h

@@ -0,0 +1,25 @@
+#ifndef URDF2PHYSX_H
+#define URDF2PHYSX_H
+
+#include "Bullet3Common/b3AlignedObjectArray.h"
+#include "Importers/ImportURDFDemo/URDFJointTypes.h"
+
+namespace physx
+{
+	class PxFoundation;
+	class PxPhysics;
+	class PxDefaultCpuDispatcher;
+	class PxScene;
+	class PxCooking;
+	class PxArticulationReducedCoordinate;
+};
+
+struct UrdfVisualShapeCache2
+{
+	b3AlignedObjectArray<UrdfMaterialColor> m_cachedUrdfLinkColors;
+	b3AlignedObjectArray<int> m_cachedUrdfLinkVisualShapeIndices;
+};
+
+physx::PxArticulationReducedCoordinate* URDF2PhysX(physx::PxFoundation* foundation, physx::PxPhysics* physics, physx::PxCooking* cooking, physx::PxScene* scene, class PhysXURDFImporter& u2p, int flags, const char* pathPrefix, const class btTransform& rootTransformInWorldSpace,struct CommonFileIOInterface* fileIO);
+
+#endif //URDF2PHYSX_H