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/model/LineColumnModel.java

@@ -2,6 +2,7 @@ package org.artisanlogiciel.games.maze.model;
 
 import org.artisanlogiciel.games.maze.Brick;
 import org.artisanlogiciel.games.maze.MovesProvider;
+import org.artisanlogiciel.games.maze.Position;
 import org.artisanlogiciel.games.maze.WallsProvider;
 
 public class LineColumnModel
@@ -40,6 +41,10 @@ public class LineColumnModel
         return c;
     }
 
+    public short getWalls(Position cell) {
+        return getWalls(cell.getX(),cell.getY());
+    }
+
     @Override
     public short getWalls(int x, int y) {
         return (short) (