Remixed Parametric Loose Filament Spool Holder

Remix of [Parametric Loose Filament Spool Holder](https://www.thingiverse.com/thing:2143718) by anotherhowie. Perfect for filament samples that come without a spool. The attached files are spools that fit a 50 mm (diameter) Ultimaker spool holder. Two of them fit on the same axle for a total width of 56 mm.

You can always use the Customizer or tweak the .scad file for other dimensions.

Changes:
* The diameter of the hole (initially 51 mm) is used as parameter rather than the diameter of