1.630 Update - roof corners

Roof corners are finally in! So much work for such a small addition. Still needs a few edge cases fixed but it's pretty close overall. Feedback on this would be helpful.

- triangle roofs now halve adjacent walls

- added mixing table

- added fluid switch pump

- fixed a copy-paste offset bug with triangle roofs

- water pumps and fish traps can now be placed anywhere in the flat scene

Expect another patch with the latest Rust changes next week.