A bit of code cleanup in SimpleRenderer.
Accessor for sprite registration point.
Stubbing out a TriangleRenderer and performance comparison.
RendererTest benchmark for TriangleRenderer.

Can swap between triangle and simple renderers at runtime.
Noticing a huge, unsurprising, performance gain with
TriangleRenderer on mobile devices.
API consistency between Renderer types.

render() is the method by which they render.
sort() is the method by which they sort.
RendererTest sample cleanup and use of sort.
More interesting sort order.
Using lower precision color in TriangleRenderer (ColorA8u).

GL doesn't know finer grained color in any case.
Starting on a new SpriteTest sample.

Added a shared_assets/ directory in samples so we don't need
to duplicate things across each sample.

Beyond being examples these are all set up to make sure things
are behaving properly, of course. Hence the name Test.
SpriteTest does a few things with Sprites with two renderers.

Used to get Sprites working with both Triangle and Simple renderers.
Sprite updates are all in implementation, but make the new renderer
work well. Using a flag to determine when vertices need updating.
Removed old sprite sample.
Notes on SpriteTest purpose.
setLayer shadowed in Sprite.

Calls both versions of setLayer in the parent classes.
Normally, I think you should just support one renderer type.
Put TriangleRenderer into pockets:: namespace.
Updated RendererTest to be more flexible for future.

Mostly merged changes from the vbo branch, though didn't grab
the VBO-based renderer. It didn't provide enough performance
increase to justify the additional management work just yet.
Ignore .xcuserdatad files.