pidp11/70 switch

Replacement knob for PiPD-11/70 kit from Obsolescence Guaranteed. This is a remix of https://www.thingiverse.com/thing:4460494, adding a knob style closer to that of a later PDP-11/70, away from ve7it's style I think of as primarily from PDP-11/45 and earlier models. There were a lot of PDP-11/70s made, and I've seen at least one with the older knob, so it's hard to say what's definitive, but this feels more authentic to me. The last picture, with the dust specs, is from a real PDP-11/70 and is what I used for reference.

Other changes include: a threaded hole for a #6-32 set screw, a friction-fit option (with a tiny tension flap inside the shaft hole), adjustable set screw height on the shaft, and improved steeping on the older knob style.

The tension flap requires high resolution (I used 50 micron, but 100 micron should be ok), so you'll need either a resin printer or a well tuned FDM printer for this option.

The threaded set screw shaft requires the BSOL library, and BSOL is not a