SL-18190 Cleanup -- convert some vec4's to vec3's (as they really are), remove some unused glsl files.

SL-18190 Fix alpha not playing nice with water surface by split LLDrawPoolAlpha into two passes, one above water, one below water, and clip against water plane.  Currently brute forces two complete alpha passes, still need to cull against water plane and add support for fullbright shaders.

SL-18190 Use funky distance based error correction only on water surface (revisit for general use later).

SL-18190 Move water shaders to class 3, add debug stub for underWaterF.glsl, make underWaterF and softenLightF apply water fog in linear space.

SL-18190 Temporarily disable occlusion culling by default -- not compatible with depth buffer management changes.

SL-18190 Water shader WIP.  Better parallax correction for sphere probes.  Reduce probe memory footprint.  Remove framebuffer copies and move to deprecate stencil buffer usage.

SL-18293, SL-18190 -- Fix for debug displays not showing up (wireframe still busted).  WIP on reflection probe/PBR driven water shader.

SL-18239 Unify PBR and non-PBR treatment of ambient/SSAO/irradiance.  Restore SSAO to release version.

SL-18190 End of linear space odyssey -- just eat the conversions in atmosphericsFuncsF for sunlight and additive, but leave linear ambient in tact.

SL-18190 WIP -- Take 2 on linear space windlight (more methodical approach -- make desired interface but brute force color conversions). Placeholder PBR water and move to deprecate forward rendering shaders.

SL-18190 WIP - Windlight to linear space proof of concept, better parity between release viewer and materials viewer when reflections disabled.  Avoid run-away probe ambiance.

SL-17705 Backwards compatibility pass.  Support OpenGL pre-4.0 by disabling reflection probes and anti-aliasing.  Get render parity with current release viewer when reflection probes are disabled.

SL-18190 Reduce banding (stay in linear space as much as possible, increase precision of reflection probes).  Faster radiance and irradiance map generation.

SL-17701 WIP -- Correct color space management for base color and emissive color factors and textures.  Support for double sided alpha blended PBR materials.

SL-17701 WIP -- Cleanup/refactor PBR lighting implementation and get parity between deferred and alpha passes for sunlight and IBL.

SL-18095 Add tangents to mesh assets so we can calculate mikktspace tangents in the mesh's original coordinate frame.