[REFACTOR] Completed move generator code
[REFACTOR] Completed move generator code

The old methods that were stored in chessboard.py have now been moved
over to movegenerator.py. During the refactoring, the methods that
determine the castling, en passant, legal moves and basic moves all
got cleaned up and optimised.

kmiller96/Quark-ChessEngine,kmiller96/Quark-ChessEngine,kmiller96/QuantumChessEngine