Add command line interface

Can be useful for setting up shell scripts or doing basic exploration.

See [centralpy](https://github.com/pmaengineering/centralpy) and [Briefcase](https://docs.getodk.org/briefcase-using/#working-with-the-command-line).

Start by reviewing the centralpy project and Briefcase's command-line documentation linked in the issue. Define the CLI's setup-script and basic-exploration scope before locating an entry point in pyodk. Done should mean that the agreed command-line workflow is implemented and usable for those stated purposes.

Written by the indexing model from the issue text.