Allow one to be notified to create an account for autoflagging

[honnza]

When Metasmoke tries to use a user account to flag on a site where that user doesn't have a local account fails silently. I would like to be notified when a new site appears so that I can do the movement of clicking the magic "confirm and create this account" button on that site. Either of these is fine:

• ping me as soon as a new public (=I can register there) site is discovered in the websocket (downside: could lead to large chat messages)
• ping me as soon as a report for that site crops up in Metasmoke (presumably easier to do than the above)
• ping me when MS tries to use my account for an autoflag and fails because it doesn't exist (avoids large messages, but also causes the notifications to be delayed significantly)
• confirm the creation of a new account on my behalf when one of the above occurs

Detecting new websites would also be useful if we ever want to have presence on every site's meta.