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/XYGridIterator.java

@@ -0,0 +1,46 @@
+package org.artisanlogiciel.games.maze;
+
+public class XYGridIterator {
+
+    final static Position stepX = new Position(1,0);
+    final static Position stepY = new Position( 0,1);
+
+    Position min;
+    Position max;
+
+    Position next;
+
+    public XYGridIterator(Position min, Position max) {
+        this.min = min;
+        this.max = max;
+        reset();
+    }
+
+    public void reset()
+    {
+        this.next = new Position(min);
+    }
+
+    public boolean hasNext()
+    {
+        return next != null;
+    }
+
+    public Position next()
+    {
+        if ( next != null)
+        {
+            Position current = new Position(next);
+            next.doTranslate(stepX);
+            if ( next.getX() >= max.getX()) {
+                if (next.getY() < max.getY() - 1) {
+                    next.setX(min.getX()).doTranslate(stepY);
+                } else {
+                    next = null;
+                }
+            }
+            return current;
+        }
+        return null;
+    }
+}