Add in more model changes around execution environments

- a new unique name field to EE
- a new configure-Tower-in-Tower setting DEFAULT_EXECUTION_ENVIRONMENT
- an Org-level execution_environment_admin_role
- a default_environment field on Project
- a new Container Registry credential type
- order EEs by reverse of the created timestamp
- a method to resolve which EE to use on jobs

awx/main/models/execution_environments.py

@@ -2,16 +2,15 @@ from django.db import models
 from django.utils.translation import ugettext_lazy as _
 
 from awx.api.versioning import reverse
-from awx.main.models.base import PrimordialModel
+from awx.main.models.base import CommonModel
 
 
 __all__ = ['ExecutionEnvironment']
 
 
-class ExecutionEnvironment(PrimordialModel):
+class ExecutionEnvironment(CommonModel):
     class Meta:
-        unique_together = ('organization', 'image')
-        ordering = (models.F('organization_id').asc(nulls_first=True), 'image')
+        ordering = ('-created',)
 
     organization = models.ForeignKey(
         'Organization',