* wip: upgrade to webgl2
* update shaders to version 300
* fix index for texture must be constant in webgl 2
* remove npot
* fix naming conflicts of using texture previously
* fix wrong internal format in float textures.
* fix depth texture format
* fix texture enabled define
* fix instancing
* fix some cases
* fix some case use extension
* fix frag depth
* tweak
* generate mimap for NPOT texture
* remove debugger code
* fix alchemyao case
* fix ssr case
* not generate mipmap in compositor by default.
