Adds the ability to automatically save gwpopulation data products to popsummary format.
Some working notes:
Currently only saves hypersamples and parts of the metadata.
Popsummary has a single metadata field for models (i.e. there's no field for vt models). Tentatively, I've just prepended 'vt:' to the string for each vt model, and then added these to the popsummary model list.
Adding most of the data products to the file should be straightforward, but some metadata (e.g. hyperparameter descriptions) as well as draws from the PPD will require additional inputs/computing.
Have added a toggle that allows for the popsummary re-formatting to be turned off. Considering this reformatting doesn't delete any old data products and is just a quick post-processing step, this may be unneccesary.