Implement castling
Restore rook position after castling
Test move equality
Add test coverage for the piece class
Add tests for bitboard
Use FEN as string representation for bitboards
Add missing return to was_into_check
Introduce move generators as sugar
Bitboard.from_fen is not needed
Let bitboard provide real implementations
Implement more efficient pseudo legality check
Revoke castling rights when rooks are captured
Use pseudo legal move count for mobility evaluator