Yet another planetary model generator.

There are a lot of planetary models out there, but few seem to be designed to be modules easily integrated into a larger system.  Hopefully this is generic enough to be used for that purpose.

A helpful online compound planetary gear calculator is at:
https://planetarygenerator.mateuszdrwal.com/

Since makerlab doesn't allow shared user libraries, I had to combine a bunch of the source files into one giant scad file.