No more auth_user_ in lists and xnetlists.

No more auth_user_ in lists and xnetlists.
Add email in account table.

TODO: have function to build a fetch data for a batch of users
   eg: User::getUsersFromEmails(array $emails, $prefill = true, $sortby = null),
       User::getUsersFromUIDs(array $uids, $prefill = true, $sortby = null)
Would be very cool to reduce the number of SQL queries.

Signed-off-by: Florent Bruneau <florent.bruneau@polytechnique.org>