Customizable Spool Adapter

~~~ You might also want to consider my Universal Spool Hub Adapter. ~~~

I use filaments from many different manufacturers, and was disappointed when they all used different spool sizes/widths. I have a Flashforge Dreamer and am using @BaronWilliams' OmniStands with relish, and so decided to come up with an OpenSCAD-designed spool adapter that lets you set the adapter dimensions so you can make a compatible hub.

The modifiable parameters include:
- Height (length) of the adapter
- Outer d