-finished  basic cell painting in grid cell widget
-location of cell image is still a little wong
-finished restructuring of TicTacToeGridWidget.could no find any regressions in  the visual inspection
-next step is to factor selection into the new sub widget
-implemented coordinate system converter to improve  readability
-corrected typo
-introduced coordinates in public interface
-corrected typo
-factored hit test in grid cell widget
-refactored coordinate transformation to be implemented by the transformed objects. This makes the coordinate system and the transformable objects  conform to the OCP
-made use of double dispatch to enable the mobility of code
-refactoring/naming
-refactoring/naming