Atlas Change Gear Holder

Change gear holder for Atlas 10F Change Gears - modelled after the original Atlas pick-o-matic change gear holder, but with cutouts and labelling for the standard Atlas 10F manual gearchange set of gears.

Uses a slightly modified version of https://www.thingiverse.com/thing:3317652 to generate the gear slot cutouts

Also included is a separate holder for the basic feed gears that are standard in the feeder leadscrew assembly, to hold them when removed to implement alternative gearings.