Min skin brightness

[dascott]

Feature: Either by default or with a server flag, limit the available skin colors to some arbitrary brightness. (around the 30% mark, I'd say)

Why: It seems the most popular color for deathmatch is jet black. As a player there's nothing I can do about this on dark maps except be grateful that I can see their helmet. Letting people set their skins so dark is basically a built in cheat - even the player who was lucky to draw indigo in OG Doom was more visible.