Add reverse that allow to switch interior/exterior of a labyrinth

- invert create a new labyrinth walls are path of previous.
  - grow then new labrynth is bigger, else shrink.

java/org/artisanlogiciel/games/maze/MovesProvider.java

@@ -0,0 +1,11 @@
+package org.artisanlogiciel.games.maze;
+
+/**
+ * Get model represented by possible moves
+ */
+public interface MovesProvider {
+
+    /** return possible moves from this position */
+    short getMoves(int x, int y);
+
+}