Collision model update for palm and forearm



To avoid self-colliding palm was updated so that thumb does not collide with palm. More box added but still simpler to check than a thousand-face mesh.
The wrist mount was not covered by a collision object, this means a planning algorithm would accept to penetrate the between the forearm and the wrist joint. A box was added to the forearm (different box for muscle and motor to cover the mount and avoid self collision with the palm.

used sr_description/test/tests_hand.sh to verify each existing model for consistency with new collision model
![new_palm-wrist_collision-muscle](https://cloud.githubusercontent.com/assets/6583181/5321797/d6a845f6-7cbe-11e4-986c-97e9d3c1376e.png)
![new_palm-wrist_collision](https://cloud.githubusercontent.com/assets/6583181/5321798/e1ea33de-7cbe-11e4-95e7-74862cebc61b.png)

started simulated hand in gazebo and no collision or vibration observed.