[Experimental] Beta version of the rock-ros bridge

The Rock/ROS bridge is in a state that allows it to be used. It probably
still has some issues, but in our tests (unit and more hands-on), it works.

It requires you to use the master branch of rock. This code will move to
the next branch in the next few weeks.

The documentation can be found at:
http://rock-robotics.org/master/documentation/ros/