1.602 Update - watchtower

7/18 Edit: Fixed some overlap bugs and added a move option to the Copy tool.
- added the watchtower
- changed the research table collider to allow boxes underneath
- big increase in saving speed (was patched in recently)
- made some improvements to loading speed
- fixed roof overlap not working correctly
- fixed camera moving when merging a file
- fixed a couple bugs with numbers over parts in stability mode
- fixed an issue with repeated use of long foundation extends causing a gradual change in rotation
- refineries can't be placed underwater