Changelog:
- 4 new gears tiers, with less friction, and higher speed
- 2 new machines to create metal gears:
  - create metal cylinders on the forge and cut them with the table saw
  - use metal disks to create gears on the gear maker
- you can make splitters with pipes like this: https://i.imgur.com/ajHzEWc.png
- you can take the content of a pipe with 'R'
- you can lock a pipe output with 'R'

Fix:
- belt rendering bug
- belt can be linked without any distance restriction
- couple can be wrong on some cases if a big gear is connected to a smaller gear
  with a belt