[BOX] Make the Vox trading post actually usable as a trading post

Created by: Exxion

So, the trading area of the Vox trading post was previously... a bit odd. It was impossible to move anything from one side of the wall to the other without contaminating the entire trade processing room with filthy oxygen. Notice how all doors are single doors.

This was annoying, at least to me. So I fixed it. Items can simply be thrown through the airtight flaps onto the table opposite each chair. The airlock at the top is... a bit of a bad method, I admit, but airlock controllers don't appear to support movement between atmosphere types, just atmosphere and vacuum. That airlock is really just two doors set to close quickly with a scrubber and vent between them. It does seem to work well enough to prevent contamination of the processing room, though, at least with reasonably low usage. Oh, and there is one change in the vault room just above the screenshot. I had to rearrange the pipes slightly, so now the vent in that room is fed from the hallway beside it rather than the processing room.

Fixes #2951 (closed)