Verify e-mailaddress *before* creating account

[matthijskooijman]

Currently, when creating an account, a verification e-mail is sent, but you are already immediately logged in (and can log in with your new password), even before your e-mailaddress is verified.

It might be better to require e-mail verification before allowing login (easier), or even before creating the account (might be more tricky, if allauth does not already implement this).

This is not a very big deal, but once we show registration lists to all logged in users #86, it might be slightly more important to require verification.

One alternative would be to only specialcase the registration list view and hide it if your e-mailaddress is not verified.