Update api docs to better describe tokens

This better describes what we mean by `token` as a parameter in `verify_password_reset_token` and `reset_account_password` password application methods.

@rdegges One more thing...do you think we should emphasize in the docs that the correct method to use here is `reset_account_password`? Since this was added to be able to do the reset in one call, rather than having to generate, send, verify a token in separate steps? It was my understanding that `reset_account_password` essentially made the manual steps private API, in a way.