New framework and rendering features

* Added debug snapshot options (with difference mode)
* Added "feature" toggles
* Multitasked, stateless shader compilation (todo binary caching)
* Lighting LUTs based on Epic Unreal Engine 4.0 / Brian Karis and John
Hable work
* Fixed cubemap SRVs
* Obj loaded file binary caching
* Half res bilateral upsampling simple "framework" / helpers
* Half res ssao
* Cubemap GGX importance downsampling
* "Physically-inspired" screenspace reflections