Improve Landing as Guest: Modify the settings panel so that it doesn't invite users to reset their password using a password they don't know.

[lampholder]

The details of the new guest experience for Riot are on the project plan: #59

If we enable users to create new accounts without submitting passwords, we need to make this bit of UI in the user settings pane still make sense:

This should either present a mechanism to set the password inline, or launch the same modal you'd get from clicking the 'complete registration' nag button.

If we implement it inline, at the bare minimum it should look like this:

Outstanding tasks:

• Consider the wording for the above - we want something that walks the fine line between encouraging and alarming, informative and... overinformative. People should ideally know that if they don't provide a password and their browser loses its session information then they've lost access to their mxid permanently, but this could be a very alarming concept to hit someone with.
• Decide on whether we do actually want a modal for this at all, or if we should just direct all new users to this settings pane to compete their registration.

[lampholder]

Opened this on the wrong repo :\