Easily create multiple admins

[milescalabresi]

It would be a nice quality-of-life improvement to have either a way to bulk-add admins (for new batches of team members) or at least the an "add another" button after making an admin at the /myesp/makeadmin page. Currently, it just says "so and so has successfully been added" and then no button to do the operation again for someone else. The submission is cached, so even refreshing the page doesn't solve it. Requested by Clark