Readds slime and AI corpse to box away

They now appear correctly, and without interfering with other parts of
the game.

Fixes turrets and their turnie offie things so they work.

Still to do: Readd window clue to bomb test area. Somehow it got removed
from the object's description.
Merge pull request #2625 from Tenebrosity/box2550Away-update

Readds slime and AI corpse to box away