Need to fix things like mechanoid threats arriving through the roof of a cave 80m underground.

It might be worth doing something about pawns being trapped because they decided to walk over the mining shaft.
Maybe increase its pathing cost or something like that, idk. They'd still walk over it if there's no other option (unless you use CE?) but that's fine.

Comment from sindri42:
```
Warning: you cannot easily move any NPC between layers. That means you need to handle prisoners on the surface, and anybody who temporarily joins you for a quest needs to stay on the surface layer because if the quest ends while they're still underground they will not be able to find their way out and you won't be able to force them onto the mineshaft for transport.
```

It may be useful to add a way for pawns to escape the mine if trapped underground. They do detect they are trapped I think, the game messages "pawns are trapped and will dig their way out" but they can't and just sit there. They could instead be told (by the mod code) to start a "job" to force their way to the underground lift and use it to go up.

Notice: the maintainer, Mlie, intends to update this last-ish in his todo list. The updates will be officially in 1.5 only so I will have a copy of the 1.4 version dll in my forked repo for anyone who wants the changes in the earlier version.

Someone mentioned wanting to send power from a lower layer to the surface. That sounds legit but it would probably be a pain to make all of the layers use the same power state. Might be resource intensive.