oad_dm17ish-a1 (The Very Long Yard) addon

Another retrieval from OA SVN r951, and yeah, there's already wrackdm17 in the base game. However, this is the map from which that map was inspired by. There's no need to describe the layout, it's q3 friggin dm17. I've cleaned up the map, added SFX and three easter eggs. Let's see if you can find them. :3