Single meds entrypoint for command line tools

[tompollard]

It would be nice to have a single entrypoint for the meds command line tools. e.g.

meds convert --from omop --to meds [OMOP_PATH] [MEDS_PATH]
meds convert --from meds --to omop [MEDS_PATH] [OMOP_PATH]
meds convert --from mimic --to meds [MIMIC_PATH] [MEDS_PATH]

This would be more flexible and enable a single help command meds --help. Not sure how best to manage a single entrypoint across multiple repos.

@rafgia mentioned that he was interested in exploring possibility of converting from MEDS to other formats (e.g. MEDS -> MIMIC). Restructuring entrypoints might be an early step in implementing this?

[EthanSteinberg]

Yeah, this seems like a really good idea.

I probably wouldn't do a single entrypoint for meds in general, but a single entry point for meds_etl is a great suggestion.

[mmcdermott]

I think this is a nice idea, but given #50 and #51, should likely be closed for now as we are (potentially, though I advocate for) moving away from having a joint package for MIMIC and OMOP in favor of separate ETL packages per data source. Feel free to re-open if folks disagree.