Vulnerability permissions management.

Add a new command to add the new group "vulnerability-editors" programmatically.
Recognize an error in django-nested-inline devel dependency resolution and fix it.
Staff users added to vulnerability-editors group can now modify vulnerability db without superuser permissions.
How to test it: 
  - create a new superuser with python manage.py createsuperuser
  - via web remove superuser attribute to the new user and add the user to 'vulnerability-editors' group
  - login as the new user and try to use vulnerability tool (add, modify, delete some record)
  - explore 'admin' application and check the visibility of just "Functions" table.