Horizontal spool holder parts

I very much liked the concept behind [this cone hub spool holder](https://www.thingiverse.com/thing:2449600/), but I wanted to make a few changes. Here's what sets this design apart from other cone hubs:
* Four wings instead of three. Makes it easier to get a grip and to turn.
* Wings are constant thickness, not pie slices. Makes it easier to fit meat-sausage fingers while tightening.
* Nut is captured rather than glued. Easier to assemble.
* A single full sized nut is used inside each hub h