Allows cameras to be broken

Well, since breaking stuff seems so popular this dev cycle, I figured I might as well get in on the action 
(actually I've been meaning to do this for a little while now).

* Cameras can be broken by weapons, projectiles, and thrown objects.
* Adds update_icon() for cameras.
* Fixes being able to show papers to AIs through deactivated cameras.
* Fixes being able to break doors with TOX, OXY, and CLONE damage.
* Fixes #7021

Probably needs local testing.