refactoring, deploy Position and XYGridIterator

- try to use more Position instead of (x,y)
  - create PositionWithDpeth for its specific usage in path finding
- create a XYGridITerator that walk cells from grid X then Y.

java/org/artisanlogiciel/games/maze/LabyMap.java

@@ -27,6 +27,11 @@ public class LabyMap implements WallsProvider
         return getAt(x, y).getWalls();
     }
 
+    public short getWalls(Position cell)
+    {
+        return getAt(cell.getX(), cell.getY()).getWalls();
+    }
+
     public int getWidth()
     {
         return tileMap[0].length;