Allow programmatic retrieval of form answers

As a creator of a form, I need to download the answers to a form in a programmatic way, in order to retrieve, store and archive forms without human interaction.

The Flask here is already prepared to serve a public API, while form results are currently provided through authenticated user sessions.

It could be of interest to add API authentication and allow for downloading form results automatically, in so up-to-date snapshots of a form can be reused elsewhere.