Verifying email twice give you 404

[Gregoire Detrez]

If you access the link to verify a fire account twice, you get a 404 page. This seems to confuse student (Ana got a few mails about this...)

Fix: keeping the verification token around a displaying a "your account is already enabled" message

[Evgeny Kotelnikov]

Duplicate of #20.

[Evgeny Kotelnikov]

It was the other way around, actually.