Replace role system with permissions-based DB roles

Develop ability to list permissions for existing roles

Create a model registry for RBAC-tracked models

Write the data migration logic for creating
  the preloaded role definitions

Write migration to migrate old Role into ObjectRole model

This loops over the old Role model, knowing it is unique
  on object and role_field

Most of the logic is concerned with identifying the
  needed permissions, and then corresponding role definition

As needed, object roles are created and users then teams
  are assigned

Write re-computation of cache logic for teams
  and then for object role permissions

Migrate new RBAC internals to ansible_base

Migrate tests to ansible_base

Implement solution for visible_roles

Expose URLs for DAB RBAC

awx/api/views/root.py

@@ -132,6 +132,9 @@ class ApiVersionRootView(APIView):
         data['bulk'] = reverse('api:bulk', request=request)
         data['analytics'] = reverse('api:analytics_root_view', request=request)
         data['service_index'] = django_reverse('service-index-root')
+        data['role_definitions'] = django_reverse('roledefinition-list')
+        data['role_user_assignments'] = django_reverse('roleuserassignment-list')
+        data['role_team_assignments'] = django_reverse('roleteamassignment-list')
         return Response(data)