Fix group member badge claiming

Fixes #587.
Merge pull request #589 from magfest/fix_group_member_register

Fix group member badge claiming
Exposes insert_admin()

Allows users to create a dummy admin account from the command line by
making insert_admin() an entry point.

Also updates the documentation to describe the most-useful entry points
in sideboard for managing the database.
Merge pull request #8 from magfest/add_insert_admin

Add insert admin