Started to remove the linked list elements and switch to a cascading renderer.
Implemented a simpler sprite batching system, doesn't benefit from the caching
of the previous method but should still perform well. It could be improved
later by caching some of the vertices if the sprite has not changed.
Further simplification of the WebGL renderer.
* Sprite batching working
* Shaders organised into a folder with a _BaseShader base class.
* Finished removing static globals by switching the GL graphics handler to instance based.
This should make it easier to have separate render contexts later and to deal with context lost/restored events.
* Untied renderer specific data from the DisplayObject derivatives, the primary one was
Graphics which had some GLData associated with it, now it is stored in a map inside of _GLGraphics instead.

Added a port of the bunny benchmark (as adapted by Matt DesLauriers to gauge batching performance with multiple textures) :
https://github.com/mattdesl/pixi.js/tree/culling/examples/bunnybench
Fixed the issue with tiling sprites working in the GL renderer.
Tidied up some of the naming.
Moved all display objects to the display folder.
Removed any unused files.
Moved the Colour helper class to core.
Implemented the strip shader.
Implemented a new multiple texture batching system (based on ideas in the
advanced batcher by Matt DesLauriers https://github.com/mattdesl/pixi.js/blob/culling/src/pixi/renderers/webgl/utils/WebGLAdvancedBatch.js
but extended to use a sampler array).
Tidied up the shader ownership (now the individual classes responsible for rendering such as batch, graphics etc now own
their own shaders).
Removed the redundant recursion benchmark.
Removed the loop in the MultiBatch fragment shader so that it will work
in older GLSL versions.
Implemented TiledSprite rendering using the sprite batch system instead
of a dedicated renderer/shader combo. This means it will benefit from
batching, especially when using MultiBatch.
The power of two for a texture is now determined automatically and
the appropriate settings selected accordingly.
Simplified the batches by pulling out common functionality into the base
class.
TilingSprite now descends from Sprite with appropriate overrides to
ensure the behaviour remains as before.
The GL textures are now generated and updated as required, handled
and owned by the batch itself. This is the final bit of GL specific
code removed from display objects themselves, meaning that texture
instances can now be used in multiple renderer instances and it
paves the way for better handling of lost/restored context.
Added missing js file in the bunnybench example.
Destroying of textures now takes a bit more effort on the part
of the end developer - since those textures must be destroyed
explicitly by passing them to the renderer destroyTextures method.