Part 3 of the Mob Destroy Refactor, this time going through the entire
list of every ref stored up to a mob/human, and (attempting) to verify
and cleanup every possible circular ref. This PR also fixes some
mistakes made with cleaning up UI elements, namely that tgui's really
don't like it when you qdel them, and screen objects also weren't always
clearing their own references if Qdel'ed directly. There were several
niche situations too where circle refs might be retained by a mob. I
also found an issue where static lights were only cleaned up on
/atom/movable/ but actually existed farther up the chain on /atom. I
don't know if any /atoms that aren't /atom/movable ever get static
lights, but the fact that they can be needs to be correctly accounted
for.
I can't possibly have gotten all of them, but this is every single one I
could find after 3 hours of work.
VMSolidus