Add closed-loop position auto command for new drivebase

[lindsayvallen]

This will require issue #30 to be completed first, and can be based on previous year's code for inspiration.

[lindsayvallen]

This will be the inner loop of position control, where we tell the SparkMax what to do it. This inner loop will be integrated with the outer loop of PathFinder, which big picture says where to go and when.