Move All Chess Pieces Images To Chess.atlas

Move all of the chess pieces images to chess.atlas because this will
allow the images to be drawn on the screen more quickly then having
them in Images.xcassets.
Moving Chess Piece Class Access Throw Chess Board

Moving Chess Piece class to only be access throw Chess Board because
this is the class structure this is now being used since Chess Pieces
are on a Chess Board this should be the only way of accessing them.

Also, remove the unit test for chess piece because the get and set of
column are too small to test