Define basic data classes / structures that specreduce will operate on

[bjweiner]

We should outline the data structures that specreduce procedures will operate on, e.g. images, slits, traces, apertures, identify / wavelength calibration structures. And we should look at other spectro reduction packages (eg PypeIt, DRAGONS) to see if we can make the structures compatible or at least translatable if possible. @eteq and I worked on a document suggesting a set of structures during the April 2020 sprint, which is attached, in text form.

Spectroscopic data reduction data structures and procedure architecture.txt