Faster perft
Count null move as another node searched
Don't validate a position after makig a move since this is done by the move generator
Added undo command in REPL
Refactored to use anonymous imbalance function with no data arrays
Bishop with pawns endgame stub
Started with material balance
Removed unused code
Material balance and single repetition vs. triple one
Material balance for book opening and fen
Material database
Refactored evaluation to use material base
Added opposite bishops tests