Extends the SquareGridWGMap. Creates a ‘chessboard map’ in which players gain bonuses for 4-squares & borders are connected like a knight moves in chess.
Adds borders as a knight could attack for a grid created by SquareGridWGMap.createTerritories.()
Args are both ints.
setter TODO: It would be great if rowHeight & colWidth were class members (instance variables), and were set
by the width/height of these images.