ENH: Proper DB connection handling via cmdline arg

[jerdra]

The rater is still in the development sphere where it creates a .db file in the current directory - this is obviously not ideal.

Instead there should be a cmdline argument where the user may provide authentication and/or an endpoint for where the database should be created. Alternatively, Niviz may write to an existing database instead.

The feature requirements are as follows:

1. User may provide a local path, in which case a .db file will be outputted using SQLite, this is meant for local sessions only
2. A user may provide a database connection string, in which case we should require auth info to establish a connection. Niviz can look for an existing table in that database or it should create it's own if none exist
3. A user may choose not to save a persistent database, in which case an in-memory DB should be used (sqlite3)