Build a real public API

[foxfriends]

The current Rust API is... rough in a lot of places. A little bit of it I thought about and planned, but a lot more of it is just random stuff that I hacked in so I could get things moving.

• A real, usable, friendly API will be required, allowing scalar values, structs, lists, and records to be constructed without friction.
• We may want to look into automatically serializing/deserializing questions and answers (Derive questions/answers #15) and whether we want to be able to write more complex questions using this system.
• Review the serializer/deserializer and make sure they are accurate and complete. I skipped a few pieces I didn't want to do for now.