RenderTexture update

RenderTexture added (webGL and Canvas)
WebGL Render rearchitected - a little faster :)
Pivot added to DisplayObject
docs updated
grunt file updated

docs/files/src_pixi_textures_Texture.js.html

@@ -67,6 +67,8 @@
             
                 <li><a href="..&#x2F;classes/Rectangle.html">Rectangle</a></li>
             
+                <li><a href="..&#x2F;classes/RenderTexture.html">RenderTexture</a></li>
+            
                 <li><a href="..&#x2F;classes/Sprite.html">Sprite</a></li>
             
                 <li><a href="..&#x2F;classes/SpriteSheetLoader.html">SpriteSheetLoader</a></li>
@@ -288,6 +290,7 @@ PIXI.Texture.fromCanvas = function(canvas)
 &#x2F;**
  * 
  * Adds a texture to the textureCache. 
+ * @static
  * @method addTextureToCache
  * @param texture {Texture}
  * @param id {String} the id that the texture will be stored against.
@@ -300,6 +303,7 @@ PIXI.Texture.addTextureToCache = function(texture, id)
 &#x2F;**
  * 
  * Remove a texture from the textureCache. 
+ * @static
  * @method removeTextureFromCache
  * @param id {String} the id of the texture to be removed
  * @return {Texture} the texture that was removed