Automatic way to create many organizations + users at once

[allanlasser]

As we add more Sunlight members which represent groups of organizations, bringing on many new organizations at once in a coordinated fashion is challenging: it requires lots of manual coordination and intervention. We have to create a new organization, invite users to join that organization, assign admin status to certain users only after they accept their invitation, and then repeat that for each organization in the group.

Some changes that could make this easier:

1. Importing a CSV and creating organizations/invitations based on that, to reduce the manual steps needed to set up many orgs.
2. Add roles to org invitations, so that admin status can be assigned to a new user after they accept an invitation to join an organization.