Feeder subsystem

[prateekma]

Still need to figure out a lot of things w.r.t sensors, etc. so we'll hold off on that for now.
Should support moving the conveyor by one ball length.
Should be able to stop a ball right at the beginning (so getting rid of momentum imparted to the ball by the intake).

Start off with some basic subsystem logic and we can add more things as we go along.