Added Quake 2 & Quake 3 icons, updated Quake icons
Created by: Jaffacakelover
Added icons to all themes, PNG and SVG, for: Quake 2, Quake 2 Content, Quake 3, and Quake 3 Content. Update several of the Quake and Quake Content icons: Reducing vertices in their SVG files, and changing colors on some to closer match the original bronze colour.