Torso-screen-launch update

In this PR:

* Added Gazebo plugin that supports publishing video to Baxter's face in simulation 
* Added torso collision mesh
* Added launch file for visualizing Baxter in Rviz in simulation mode

Todo:
- [ ] Tweak the screen_visual link location to be better aligned with baxter's face (I worked on it for a while but its not perfect)
- [ ] Replace base_link_collision.STL with a DAE version