Merge branch 'sev/menu_icons_mipmap' into 'master'

Merge branch 'sev/menu_icons_mipmap' into 'master'

Fix blurry menu icons

Before I made Luma, new gametype and serverlist icons were added to the existing menu themes.
However, they are too sharp, which causes aliasing in-game.
Seemingly as a quick and dirty fix, some of those images are preloaded with the MIPMAP flag.

This inconsistent drawing of the images causes issues for Luma,
where the icons get too blurry (http://i.imgur.com/9mJCnJA.png).

This branch makes the following fixes:
- All server icons are either fixed or remade, so they don't need MIPMAP.
- Each menu theme can chose itself if the gametype icons need MIPMAP,
with the new theme variable BOOL_GAMETYPELIST_ICON_BLUR.

See merge request !151