target tracking subsystem

[KiraA-R]

code needs to be refactored from twin-stick drive

[jamesra]

We want a way to lock the robot's heading to a target field position (X,Y) or an angle (theta). I'd expose two methods, one sets an angle. One sets a field location. After thinking more this is probably a command and not a subsystem. It runs continuously once a user presses a button and then is disabled when the user presses another button to choose a new target or return to a manual control. This is an intermediate project that may get more advanced as it is integrated into the robot. Twin-Stick jitter problem needs to be solved before it is useful.

[jamesra]

Worked with Eric to refactor. Checked in initial code so other commands can be written to use it. Needs testing before closing.