make generate_database script

[kelle]

Use https://github.com/SIMPLE-AstroDB/SIMPLE-db/blob/main/simple/utils/generate_database.py as a model.

goal is to build database using JSON files, generate a file, starting off with sqlite file.

future options could do things like add versions to the versions table, optionally append version number to the file name.

[dr-rodriguez]

Done as part of the loaders module in #223