Add remaining_badges count to admin pages.

Adds a remaining_badges count to the index and "at-the-door"
registration admin pages. The text gets big when the number is under 50.
Change order of check-in button

Moves the check-in button closer to the attendee name to help prevent
user error.
Merge pull request #517 from magfest/85_reg_flow

Changes to 8.5 registration flow.