Documentation of the CSV-to-DB functionality

[anamileva]

We need to document the CSV-to-DB functionality and determine a structure for automatically pulling in these docs from the code.

Note: this is best done after #586 and #587 have been addressed.

[nmgeek]

The first step, loading the subscenarios with port_csvs_to_db.py seems to be documented ok. The documentation for loading scenarios could use more explanation.

[anamileva]

Thanks for the feedback, @nmgeek.

[nmgeek]

I am working through the getting started process with scenarios and taking notes. Let me know if you would like me to submit text for this.