Feature Request: Allow FIRSTONLY catab, cotab, and patab files

[billdenney]

In read.nm.tables.R, if the files read in have a different number of rows, no data is returned:

The table files associated with this run number ( ) appear
to have different lengths.

Since cotab, catab and patab in many cases just have unique data for the individual (not for each row like sdtab, etc.), it would help if xpose supported loading these files and then expanding based on the individuals (via merge or left_join).