Customizable solidoodle alternative snap spool holder

Companion piece (added 7/10): Moderately-easy enclosure for Soldoodle.

I really liked the spool holder by nlancaster, but (i) it was a bit tough to print nicely (it was my third print ever, though :); and (ii) the newer Solidoodle spools seem to have larger diameter.

Modified snap-in spool holder, that:

1. Is fully parametric! You can change mounting point, arm length, angle, clip diameter and orientation, etc.
2. Is much simpler to print (but perhaps not as pretty)
3. Adds screw counter-sink
4. Includes full SCAD source (could use some cleanup)

The outer bracket and tower could be one piece, except it's too large for the SD2 .

ChangeLog:

• 7/14: Added STLs I'm using with companion enclosure.
• 6/15: Added insets for rivets, when choosing back positioning (measured and tested on my SD2, there is some extra slack, let me know in comments if positions are off).
• 5/23: Fixed some non-manifoldness SCAD issues on towers (pls let me know if you find parameters that produce non-manifold STLs).
• 5/22: Fully parametric version, for Thingiverse Customizer. Also included additional mounting options inspired by yakwool's remix (plan to test those soon, once I get around to building a case which could use extra clearance).
• 5/20: Initial version (non-parametric).