Allow anonymous form submissions

[ehsanmasdar]

A common problem we have been seeing is that for at-event registration the user signup process often becomes a pain point. We should expose a form on a randomly generated link (such as https://registration.hack.gt/register/abc123) that displays an email/password prompt and application form inline with a submit button on the bottom. This link will be loaded on event provided laptops for walk-ins to register on. Users that submit this form should be configurably auto-accepted and auto-confirmed (this may be exposed as options on the branches see #150) and they won't have to verify their email.

[bunsenmcdubbs]

I plan on implementing this feature in 3 parts.
See #205

[bunsenmcdubbs]

@ehsanmasdar how would the "randomly generated link" work?

[bunsenmcdubbs]

Also, we can consider adding a RegistrationBranch type that supports a "confirmation-less" workflow. Not sure if "anonymous" (do not need confirmed email account) submissions should be an option or automatically enforced.

This type of work is slowly creating a reason to make workflows configurable - ANOTHER LAYER OF ABSTRACTION.

UPDATE: jk this seems like a bad idea that would lead to a lot of duplicated code for this PR.