Encode viewspace Z normal to preserve negative Z (fixes all light shifting errors, and shiny environment map errors due to lack of negative Z)

a bunch of trivial clean-ups and commentary.

Coalesced patchset.

Pathfinding visualization WIP -- add many controls for x-ray render, add lighting, and better combat z-fighting and noise from wireframes and overlays

SH-2908 Rework indexed texture rendering to use a uvec4 instead of a float for texture indices in the data stream.  Also rework gl_FragColor overrides to not collide with some odd driver implementations.