F hand lite urdf

Adds a URDF for the new Hand Lite.

Launch with:
```
roslaunch sr_hand gazebo_hand.launch set_hand_description:=1 hand_description:=$(rospack find sr_description)/robots/shadowhand_lite.urdf.xacro gui:=true
```
View in gazebo:
![gzclient_hand_lite-2014-12-18t11_59_18 015955](https://cloud.githubusercontent.com/assets/193641/5487969/ded58fe0-86af-11e4-806d-9a036a99b7b8.jpg)
Start rviz, set base frame to forearm and add a RobortModel and TF.
Rviz:
![rviz_hand_lite_2014_12_18-12_03_57](https://cloud.githubusercontent.com/assets/193641/5487973/e4fdf394-86af-11e4-81d4-7797187602eb.png)
Rviz: collisions:
![rviz_hand_lite_collision_2014_12_18-12_05_02](https://cloud.githubusercontent.com/assets/193641/5487975/e90e781e-86af-11e4-9f68-23ec9221d711.png)

Fixes #182.

Need to follow up with #184 and #183 

@guihomework - @ugocupcic said you would be interested in reviewing this one, if you have time, cheers.