Added loadFramedSpriteSheet to ImageLoader, this method allows loading uniform sprite sheets that don't need a texture packer description file .

This will allow loading frame sprite sheets and give access to each frame.
the method also allow caching of each frame

usage example

```javascript
var image = new PIXI.ImageLoader('tileset.png');
image.addEventListener("loaded", function (event) {	
	var frames = event.content.frames;  //image frames are stored here

	var terrain = new PIXI.Sprite(frames[8]);  
	//var terrain = PIXI.Sprite.fromFrame('terrain-8');  //we can use this syntax too if a frame name is provided (here the frame name is 'terrain' the frame order is 8

	terrain.position.x = 0;
	terrain.position.y = 0;
	stage.addChild(terrain);

	document.body.appendChild(canvas);

	renderer.render(stage);
	
});
image.loadFramedSpriteSheet(92, 46);

//image.loadFramedSpriteSheet(92, 46, 'terrain'); //if a frame name is provided (here = 'terrain') then the frames will be added to PIXI.TextureCache

```