- Use bash instead of sh/dash to support argument slicing.
- Default Celery worker concurrency to 0 (auto).
- Set DJANGO_SETTINGS_MODULE environment variable to make it
available to sub processes.
- Add entrypoint commands to run single workers, single gunicorn
or single celery commands like "flower".
- Update Gunicorn to use sync workers.
- Add platform template to return queues for a worker.
Signed-off-by: Roberto Rosario <roberto.rosario@mayan-edms.com>