Splittable, customizable toothbrush holder

This is a customizable toothbrush (or otherwise) holder. If you set the `split` option to true, it will generate two pieces that can be assembled together (in case your printer can't print this as large as you need), which connect via rods. You can adjust the tolerance of those for a close fit, or just superglue them together.
Another thing you'll want to adjust are the initials behind each individual holder - that's the `initials` variable.
Finally, you might want to adjust the inner and outer distance in each holder if your toothbrushes are especially thin or thick, the height of them from the bottom plate, or to (with the `apply_cutouts` variable) specify whether you want the circular cutouts in, to save material.