Fix TS offsets for good

I had suspected that the offsets were still wrong, but didn't have time to look at them properly until now.

Turns out they were a mess. I used TS' own blank01 tile as test grid and whipped the offsets into shape.
Additionally, I set okayish selection bounds for structures as temporary solution until we have proper isometric selection boxes.
Finally, the fixed offsets allowed to fix the factory exits as well.