Small refactors
REST deletes check if there are associated children.

- Create helper methods on a model object to know if there are any associated children to it
- All REST deletes now check if there are any associated children and if so return a NonEmpty error code
- V1 REST deletes are not affected
- Specs now have a one_to_many_ids_without_url which includes all associations which need to be checked if they are deleted but dont have a sub url
Recursive deleting of all models.

- Note that QuotaDefinition will delete the entire Organization
- Note that Space will only nullify the Default User