Add organization deletion workflow

[dankolbman]

Because deletion of an entire organization involves a cascade of deletions to the studies and then documents, care needs to be taken when deleting an organization.
The first option is to implement a deleteOrganization which organization administrators may trigger. This mutation would schedule a deletion task for some number of days after being triggered which would automatically run and remove the organization and all related models.

The second option is to have a requestDeleteOrganization which organization administrators may trigger. This would notify superusers of the request to delete. The superusers may then trigger deleteOrganization on an organization which has been requested for deletion or they may denyDeleteOrganization which will unset the requested for deletion status on the organization.

The first one is the simplest solution which provides the organization owners full control over their data.
The second is more complicated and requires that we implement email notifications, superuser concepts, and a dashboard to review organizations that are requested for deletion. This also removes some power of the organization owners over their data which may be a compliance and privacy issue.