Beta release needs some code reorganization

We want a public header that can be used along with the shared lib. Ideally this is a single header or set of headers which have documentation, and only contain the public-facing interface. That would be the transactions object, attempt_context, associated constants/structs/enums. Also - we probably don't need to expose the client headers at all.

So – ponder a bit. Then, when the code is reorganized (and documented), make sure that we build the example with only the public headers and the shared lib, so we know we distribute a usable library.