Split custom_badges_really_ordered

Fixes #545 by splitting custom_badges_really_ordered into add_custom_badges and shift_custom_badges.

Keep in mind that the logic has flipped - shift_ and add_ need to be True by default.
This could be based on ``SHIFT_BADGES``, since we'd infer that if it's okay to shift badges then that implies the order hasn't been placed yet, so it's not too late for an admin to edit the name on someone's badge.