added some more clarity to the notion of starting months, ending months, and number of months. with clarity, fixed bug in the spanning functions for facility curves and material flows
updated the tables and utility modules to add all tables if they exist in the schema. this allows for auto-detection rather than relying on clients.
streamlined engine connections in the tables module
query correctly works for a single month or multiple months
updated swu and natu queries to return python floats
fixed issue in curves where the months weren't being calculated correctly
adds ability to query SWU and naturalU curves based on the enrichment facility. updates the table addition to automatically query if a table exists, and then to map to it if it does.