11/18 filled out some board fxns - John Marinelli

filled out:
Board::Board
Board::isSpaceEmpty
Board::getPieceOnSpace
Board::addPieceToBoard
Board::removePieceFromBoard

added public functions:
Board::addPiece (missing 1 error-checking capability)
Board::removePiece

also changed the 2D array to an ArrayList for l337 member functions