Improve function call perf and/or offer users more options to limit their results

[flaneuse]

When you call functions like getAdmn0() or getAdmn2ByCountry() the function is slooooooooow since it has to make a bunch of calls and returns a lot of data.

Would be nice to offer the users the ability to limit the query to a smaller subset of the data to help make it easier to return data faster. Potential options could include narrowing by date range, mostRecent, returning only a subset of fields...

Might also be worth double-checking that the function is as fast as possible. You're probably API-limited, but if it could be faster, that'd be nice. (low priority)