Convert internal pubsubs to ros [3 pts]

[SimLeek]

While I don't like the ros catkin stuff, we should be able to publish to a live ros-server if it's up without dealing with that.

The default ros storage formats should already be able to store and send images.

We also need to make sure we're only sending some of the internal pubsubs to ROS, based on the user's selection. A 'publish_to_ros(name)' function on the video stream class, and 'receive_from_ros(names)' on the display class should work.