Parametric Filament Clip

This is a slight rework of the same named item by qubit01.

The differences are:
* I made the wall thickness of the filament holder portion automatically calculated
* Re-formatted the file to match my style preference.
* While I was at it, I fixed the subtracted shapes by making them bigger by 1mm, and moving down by 0.5mm so they stuck out by 0.5mm on both sides. Because there was zero overlap between the primary and subtracted shapes, this causes a “skin” of thickness 0 which is usually considered a bad thing in modeling, and is visible on screen when compiling (F5) and can also result in artifacts in the resulting mesh under some circumstances.

The STL files I generated have the holes for the filament set to the exact size. If it's too tight, I just ream the holes out with the appropriately sized drill bits (e.g., 1/16 or 5/64 for 1.75mm).