Vertical Spool Drawer and Stand Remix

This is a remix of https://www.thingiverse.com/thing:4867715 and https://www.thingiverse.com/thing:4861706 to reorganize the openscad into individual modules and make it possible to generate one stl file for one part. It also adds some additional bits I found I needed when trying to turn an old style small and wide Octave spool into storage. The side weren't flat, they were actually shallow cones, so I added a ring to the outer edge to put under the guides. Also the edge of the side has a raised bead, so I added an extra "step" to the stands to hold it away from the side to clear the bead (and the outer edge of the cone shape).

I moved the user variables out of the common files so you can make a file with just the variables which then includes the common (see old-octave.scad for an example), then that file can be included in a separate file to create an instance of a single module to create an stl for just one part.

I've included all the definitions for the old octave spool I used and the stl files that generated more as examples than because I expect people to have these spools laying around.

More details may appear at http://tomhorsley.com/hardware/corexy/gallery-spool-drawer.html