Add destroy methods to Ninja Body, AABB and Circle

The Sprite.destroy() method calls the Body’s destroy() method if a body
exists. If using Ninja physics, destroying a Sprite will not work,
since the destroy method wasn’t implemented in Ninja’s Body.

Also added destroy() methods to Ninja’s AABB and Circle. Tile already
have a destroy() method.

src/physics/ninja/AABB.js

@@ -1002,6 +1002,16 @@ Phaser.Physics.Ninja.AABB.prototype = {
 
         return Phaser.Physics.Ninja.AABB.COL_NONE;
 		
+    },
+
+    /**
+    * Destroys this AABB's reference to Body and System
+    *
+    * @method Phaser.Physics.Ninja.AABB#destroy
+    */
+    destroy: function() {
+        this.body = null;
+        this.system = null;
     }
 
 }

src/physics/ninja/Body.js

@@ -417,8 +417,23 @@ Phaser.Physics.Ninja.Body.prototype = {
     */
     deltaY: function () {
         return this.shape.pos.y - this.shape.oldpos.y;
-    }
+    },
 
+    /**
+    * Destroys this body's reference to the sprite and system, and destroys its shape.
+    *
+    * @method Phaser.Physics.Ninja.Body#destroy
+    */
+    destroy: function() {
+        this.sprite = null;
+        this.system = null;
+        this.aabb = null;
+        this.tile = null;
+        this.circle = null;
+
+        this.shape.destroy();
+        this.shape = null;
+    }
 };
 
 /**

src/physics/ninja/Circle.js

@@ -2606,6 +2606,16 @@ Phaser.Physics.Ninja.Circle.prototype = {
         }
         
         return Phaser.Physics.Ninja.Circle.COL_NONE;
+    },
+
+    /**
+    * Destroys this Circle's reference to Body and System
+    *
+    * @method Phaser.Physics.Ninja.Circle#destroy
+    */
+    destroy: function() {
+        this.body = null;
+        this.system = null;
     }
 
 }