Token login

[rglover]

Just set up a Mullvad account and was blown away by how slick the anonymous token-based username workflow functions. This would be insanely easy to add to Joystick. Possible API:

// Signup is just to generate a token:

const token = await accounts.anonymous_token();

// Login is just to pass the token instead of a user/pass:

accounts.login({ anonymous_token: 'abc123' });

Everything else should be roughly the same as far as database. Maybe just a few tweaks.