Enhancement: Various missing features and bugs with VRAD

[lunairekitty]

What would this enhancement be for?

Hammer

Describe your enhancement suggestion in more detail

Add/fix various missing features of VRAD from other games

1. -softencosine: Softens coloured lighting so it blends more accurately. (Slammin' Hammer, Garry's Mod)
2. -StaticPropLighting: Always uses -fast level of sampling, ignoring -final and -extrasky. Fixed in VRAD++.
3. -StaticPropSampleScale: Only affects indirect lighting, not direct. Fixed in VRAD++.
4. -propambient: Prevents VRAD from generated ambient cubes inside of props. (VRAD++)
5. -threads: Limited to 32 threads maximum, upped to 64 in VRAD++ (VRAD++)

[lunairekitty]

Note: 1 and 4 are addition suggestions. 2, 3, and 5 are bugs.