Add djangorestframework to requirements.
Return systems as URLs from interfaces.
Make some related objects links and add label, domain fields.
Adjust API URLs to match Cyder UI URLs.
Clean up dynamic interface API serializer.
Protect user's API keys from other users, tidy up.
Merge branch 'test_django-rest-framework2' into api_user_detail_view

Conflicts:
	cyder/api/authtoken/templates/authtoken/token_detail.html