Promoting BlankBoard's addPiece method to an actual required method for all Boards.

We need this for our bug fix.
Clean-up.
Attempts at debugging which leads to code with better parentheses.
Failures down to 6 by modified 'undo' procedure.
Adding null provisions to the addPiece method of Board.
Down to 1 by re-enabling CastleFilter.
Clean up debugging printlns.