Pre-set badge status for new attendees

There's no specific reason to make the admin save the attendee first and
then have to go back and change their status, so I've removed the check
for is_new.
Adjust badge status workflow

Further adjusts the workflow to fix a case where, if you saved unrelated
attendee data, the system changed the badge status for you. Now it ONLY
updates if the attendee's amount_paid gets altered.