copy/move heightfield files around (part of pybullet_data)

prepare for heightfield support in pybullet (first step, needs a bit more)

examples/Importers/ImportURDFDemo/UrdfParser.h

@@ -55,6 +55,7 @@ enum UrdfGeomTypes
 	URDF_GEOM_PLANE,
 	URDF_GEOM_CAPSULE,  //non-standard URDF
 	URDF_GEOM_CDF,      //signed-distance-field, non-standard URDF
+	URDF_GEOM_HEIGHTFIELD,   //heightfield, non-standard URDF
 	URDF_GEOM_UNKNOWN,
 };