RP-248 Migrate Husky base to ros_control

Migrate to ros_control using horizon C++ API

Fix #5 #3 
The control loop is supposed to go on its own thread entirely, free of comms stuff or anything else non-realtime that could block it. I'd suggest putting it on a control_queue with a control_spinner, and moving the diagnostic updater to the main thread. Put the hardware access logic on the main thread as well, with buffers to pass data to and from the controller; see: http://docs.ros.org/indigo/api/realtime_tools/html/namespacerealtime__tools.html

This isn't _really_ necessary in this instance, but it's a good habit to be in with ros_control.