Validate s3

[rajeee]

Partially addresses #53 .

Pull Request Description

• An option is added in the project yaml file to specify the s3 upload folder name.
• Validates that there are no existing data in the s3 upload location.

Checklist

Not all may apply

• Code changes (must work)
• Tests exercising your feature/bug fix (check coverage report on CircleCI build -> Artifacts)
• All other unit tests passing
• Update validation for project config yaml file changes
• Update documentation
• Run a small batch run to make sure it all works (local is fine, unless an Eagle specific feature)

[nmerket]

@rajee This has been here for a long while and looks like it could take some work to resolve conflicts. Do you still want this to go in?

[rajeee]

@rajee This has been here for a long while and looks like it could take some work to resolve conflicts. Do you still want this to go in?

@nmerket Yeah, I think I was waiting on the yaml file refactoring before merging this. I guess, that refactoring is yet to happen? I think things are still duplicated between postprocessing and aws spec.

[nmerket]

Sounds good. I'll leave it alone until then.