merge #1052, fix EJECTA issue where renderbuffer isn't reset

merge #1113, reuse code in autoDetectRecommendedRenderer

merge #1171, use gl.isContextLost()

merge #1176, fix regression in RenderTexture

merge #1193, fixes for Base Texture loading code

merge #1216, small getBounds optimization

merge #1310, log type when not chrome

update extras to new renderer methods

make texture frame a setter; clear up some typos

move all render webgl code to DOC

minor event target speed boost

minor style tweaks

move cacheAsBitmap to DOC

move primitives back into a separate module

reorg webgl utils; move primitives to core; refactor shape types

successful removal of globals and _dirty flags

Lots of core renderer-related updates ...

- Removed `Stage` completely from core lib, in favor of directly rendering
  DisplayObjects
- Removed rendersession from core lib
- Rewrote WebGL managers to be more DRY and have a common base
- Rewrote Shaders to be more DRY and have a common base

fix require paths for browserify

initial move to new module folders