AIs can interact with fire doors

AIs can now open and close fire doors if they are powered and unwelded.

This is done so the AI could more freely manipulate the doors without needing to use a fire alarm each time. It would let them seal off areas without triggering the annoying alarm, and also let them close firedoors that one guy with a crowbar opened up.
Merge pull request #875 from Ikarrus/fireai

AIs can interact with fire doors