added scavenge to mission file

Edit: Scavenge is currently broken. I originally made this map before the steam workshop even existed.
So it's been a long ass time since I've even touched it. So maybe I uploaded the wrong version.
I'll try looking into it when I have some spare time.

Attempt to fix scavenge mode

added missing textures

Uploaded version 4.0 from 2/25/2013 (last version on gamemaps.com)