Add feedback controls for both locomotion motors in microcontroller-side program.

[bsawka]

We've had a pretty consistent problem over the past year or so where C1C0 doesn't really drive straight, and I think I've diagnosed the problem - to summarize, despite the two motors having closed-loop feedback controllers built in to their drivers, they currently are treated as the only system in the universe and have no information about the other motor. What's necessary is to provide feedback from each motor to the microcontroller sending PWM signals to each driver, and adjust the signals using some robust controller design. There are many ways to approach this, and it could be quite the undertaking.