Adding support for PhantomX Pincher arm

I've tested this successfully with PhantomX Pincher.  (Also requires new config/URDF in Turtlebot which I've pushed to Corot).
I would suggest not making these parameters a one-size fits all for all joints. If constructor takes a string for namespace, you can push these parameters down to the specific joint/servo that is using this conversion. See for instance the constructor of DynamixelServo class (which namespaces servo parameters into ~joint/servo_name/parameter)