Zenko -- multiple backend

[LaurenSpiegel]

Our current deployment stack assumes a file backend. Our default should actually be the DATA=multiple option. However, with DATA=multiple, a locationConfig is necessary.

1. We should add the DATA=multiple Env variable for s3-frontend
2. We should propagate the loctionConfig.json to all of the nodes so the s3-frontend can obtain it.
3. We should use Docker secrets to store the real AWS credentials and azure credentials and might need to modify s3 to get these from Docker secrets.
4. Must be documented.