Group signup

[mmcinnestaylor]

Currently, the account registration form only accepts input for a single user. An implementation of multiuser registration exists in the codebase (src/register/views.py, src/register/templates/register/group_register_form.html ) but generates a key error upon form save. Group signup would be particularly useful for walk-in users/groups on contest day.

Ref:
https://stackoverflow.com/questions/34962398/keyerror-at-registration-value-password1/34963664