Automatically schedule an organization for deletion after all site data is deleted

Issue Summary

When a Cloud site is deleted, the organization will remain indefinitely, unless the organization admin returns to delete it.  That org cannot be deleted while there exists one or more sites within that org.

Why this is important

It's very common that when a site is deleted, the org admin simply forgets to return to delete that org as well.  This can be troublesome for organizations that return to create a new site with the same name later, since by default the org name is based on the site.  This commonly leads that org admin to have 2 or more orgs with the same name which is confusing.

Suggested resolution

When a Cloud site has been deleted by an org admin, automatically setup the org to be deleted as well, as long as there are no other sites in that org and no other configured features within the org, such as verified domains, authentication policies, etc.