Iterate the last commit. `dev_django.py` is now the hub for running a Django environment with the component's settings; it's not just for tests.

- `run_django_cmd()` can run any Django command
- command line access proxies `manage.py` (so it too can run any Django command)
- add loading error messages
- `test` is a special case where a) we want to allow specific tests (https://docs.djangoproject.com/en/1.5/topics/testing/overview/#running-tests) b) but default to `TESTED_APPS`