fix quadruped.py example. add PyBullet.isConnected() API, more friendly than PyBullet.getConnectionInfo()["connected"]
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 )