Integrating pychess python package

[coreylowman]

So this is a pretty big rewrite, so sorry for the awful diff. This PR will make it a ton easier to integrate a chess engine (like stockfish), because the python chess package has UCI chess engine interface built in. I can integrate a chess engine in another PR.

Here are the notable changes:

• Removing all chess specific code, as the chess library handles that now.
• Adding simple GPIO wrapper class called Magnet.
• Adding MotorMover class to handle moving the motors. This keeps track of the position instead of always moving back to 0,0.
• Input of moves is now done by reading in a UCI string. Promotion is now part of the move specifically (e.g. a7a8q moves from a7 to a8 and promotes to a queen).

I can run a regular chess game when commenting out the motor & magnet code, so I'm fairly confident in that. I'm not sure about the magnet & motor code though... I can't see anything obviously wrong, but you'll have to test it and let me know. :)

[bfentiman]

Thanks for the pull request. I will test it with the physical machine and update you so that you know what ends up happening with it. 👍

[coreylowman]

Sounds good - note that playing against the computer will require you to download the stockfish executable (or some other UCI chess engine executable), and then modify the path to that executable on Line 318