Refactor Elastic conf to not require S3 credentials for development deployment

[thepsalmist]

Currently, the elastic-conf service throws an error when any of the args is missing, this includes ~ELASTICSEARCH_SNAPSHOT_REPO, which is an S3 repository. As mentioned by @philbudne it isn't a necessity to have S3 credentials for a dev deployment. To do; refactor the elastic-conf to capture the above Question: Should we have a dev.sh file in private config repo to maintain any dev deployment secrets?

[kilemensi]

If we want to continue running/testing SLM in dev, using a filesystem repository rather than S3 is probably the better approach; should eliminate the need of S3 credentials in dev.

[philbudne]

Question: Should we have a dev.sh file in private config repo to maintain any dev deployment secrets?

My preference: no. People should be able to test/develop code without access to any secrets.

[thepsalmist]

Resolved in #295