HDR lighting/deferred shading

[FeepingCreature]

I think KSP should transition to deferred shading with float targets (HDR). These are my reasons:

* I think to some extent people have become used to KSP's poor lighting model, to the extent that they consider it normal.

* With deferred shading, KSP could support large numbers of small light sources more easily (small part lights become effectively free; that is, down to the cost of a (transparent) quad draw with the surface of the area affected by the light source!) Plus, any light source that throws in a thin-ish cone can be done relatively cheap as well, since you just need to draw the cone.

* Planetary landings at dawn/sunset look seriously weird. The ground is way too dark. This is, of course, because the ground is lit with boring "angle of incidence dot normal" lighting, when realistically our eyes would adjust to the low-light conditions. Fixing this does not, in principle, require HDR, since cheap tonemapping can be easily approximated, but it looks better with HDR and also requires less finetuning.

* Most of the slowdown comes from physics/CPU side. Let's give the GPU something to do. Even Intel cards can run deferred shading nowadays.