Change Chess Board Class To Use Chess Piece Class

Change Chess Board class to use Chess Piece class instead of NSInteger
because this will better represent what is on the screen.

Also, the class structure now does like this Chess Piece can only be
access throw Chess Board since a chess piece is on the chess board and
it controls the array that represents it in memory. ASimpleChessGame
class controls the Chess Board since it does the game data such as
who’s turn it is and the number of chess pieces not in play.
Fix Error When Trying To Last Chess Piece Type

Because the number of chess piece types is too low this causes an error
when trying to access the last piece type Also zero in
numberOfChessPieceTypes is supposes to be empty space/