Change login popup submit button title.
Don't close login popup if clicks Escape.
Don't show annoying "You closed the login window" message.
Make login popup actually login, at least guest login

- Include missing dependencies
- Call window.opener...handleLoginResponse() from login popup
- Call close() earlier
Don't ask about email notifications of replies, assume users want them

Assume users want email notifications if they provide any email address.
Now I can remove lots of complicated code that doesn't play well with
<iframe>s: the code opens a modal dialog inside the iframe and asks
about email, but modal dialogs in iframes are kind of pointless.
Fix bug that prevents email notifications: upgrade debiki-dao-rdb

If no email notification preferences specified, the site id is not loaded
and that prevents sending email notifications to guests.
Remove logout and login confirmation dialogs

They don't play well with iframes.