Stahl20 filenaming convention is unclear

[djperrefort]

The bsnip.Stahl20 class parses all of the spectra data files provided by the SNDB for the associated data release. However, I'm not sure what the difference is between *-ui.flm, *.coadd-ui.flm, or *-br.flm files are. This should be clarified with the BSNIP team and (if necessary) also clarified in the data tables returned by sndata. For example, if different files represent different stages of the analysis, that is something the user should be made aware of.