Generate staging task id in CC
Add 'extra' field to Services model
Stop other staging tasks for app on new staging request

Verify staging task is the latest by saving latest task id and comparing
it after completion with the one in database.
Recursive deleting of all models.

- Note that QuotaDefinition will delete the entire Organization
- Note that Space will only nullify the Default User
Merge branch 'master' into delete_models_with_deps