Fix dealer form to stop resetting badge count

The dealer form was resetting the number of badges selected every time
it was loaded. This could cause usability issues because the form is
reloaded when validation fails. This adjusts the table-badge association
code so it doesn't do this.
Assign dealer_asst ribbons to new dealer badges

There can only be one person with a "Dealer" ribbon per dealer group.
This changes the admin form so that new badges get a DEALER_ASST ribbons
instead of a dealer ribbon.
Merge pull request #850 from magfest/fix_dealer_reg

Minor fixes for dealer registration