updates for android.

ios/src/java/advent/core/GameCenter.java

@@ -67,6 +67,19 @@ public class GameCenter {
             });
     }
 
+    public void show(final UIViewController d) {
+        GKGameCenterViewController controller=  new GKGameCenterViewController();
+        controller.setGameCenterDelegate(new GKGameCenterControllerDelegateAdapter() {
+                @Override
+                public void didFinish(GKGameCenterViewController g) {
+                    d.dismissViewController(true, null);
+                    System.out.println("achievements done");
+                }
+            });
+        System.out.println("showing achievements");
+        d.presentViewController(controller, true, null);
+    }
+
     /** Report an achievement completed (100 as percentComplete)
      * 
      * @param identifier */