improve btMultiBody version of URDF reader (still work-in-progress) enabled planar joint for btMultiBody (untested) enable loading from relative path for .stl meshes
Add 'createCollisionObjectGraphicsObject' API for CommonPhysicsSetup Add 'pthread' dependency as workaround for NVIDIA graphics driver issue (see //See https://bugs.launchpad.net/ubuntu/+source/nvidia-graphics-drivers-319/+bug/1248642 )