Allow for alternate datasets in Stout JSON file and in LaTeX table

The scripts and JSON data file that handle Stout references are not designed to handle multiple datasets per atomic model, as is the case for Fe+.

This limitation is lifted in this branch. The scripts are adapted to handle multiple datasets per species.

The JSON file is updated (this is particularly relevant for Fe+), and the LaTeX tables are also updated to report the dataset name (e.g., fe_2_.nrg).

A bug is also fixed that misset the masterlist the species may be found in.