language.loader method

[nathimel]

I think the pattern in the indefinites example and the modals example can be refactored into a loader() method, which takes a CSV and a Universe and returns a list of Languages. Thought of this while drafting a summary of the demo.

Obviously this won't cover every case of how semantic typological data are encoded into CSVs, but the format we're consuming now is somewhat privileged, since its in tidy format (and CLDF?)