Update Quickstart to use sprites rather than canvas draws

[kamranayub]

I think one of the reasons Breakout is so slow on Xbox One (or my phone) is due to all the canvas drawing, rectangles and arc for ball. I was talking to Zach and he's convinced that's why the SHMUP example runs at 60fps on Xbox compared to the ~25fps for Breakout.

We should update the quick start to provide a sprite sheet to use for the blocks, ball, and paddle. Then update the demo too and see if that improves performance.

This would also introduce the Loader, Sprite, and Spritesheet, which are important building blocks of Excalibur.

[kamranayub]

From Zach:

I've got plenty of demos with abusive use of rect and arc
http://www.zachstronaut.com/lab/space-smasher.html
you could see if they are also slow
http://www.zachstronaut.com/lab/3d-canvas-galaxy-1000-pixels.html