Development

The mailing lists member sync was too elementary to
be used on production properly. This was for example
due to the single calls to MailChimp for each seperate
Contributor.

Now during sync, only updates are called to MailChimp, not
*all* contributors. Also, the batch operation is used instead
of seperate calls. Further, some query tweaks were used that
expect database calls to improve significant.

The login view is update such that the users will not get any
unexpected/unpleasant errors anymore if they don't get their
password right the first time.

Also, the redirect_url didn't work when it was given through
a GET request, which is used for example after a redirect
from the @login_required decorator.