Add CWL destBucket runtime option (resolves #2241)
Add CWL destBucket runtime option (resolves #2241)

Adds an option to specify cloud bucket endpoints for the final outputs
of a CWL workflow. This works (and has been tested) for the following
cases:

AWS S3:
toil-cwl-runner --destBucket s3://my-bucket-name workflow.cwl config.yaml

Azure Blob Storage
toil-cwl-runner --destBucket wasb://container_name@account_name.blob.core.windows.net workflow.cwl config.yaml

Google Storage:
toil-cwl-runner --destBucket gs://my-bucket-name workflow.cwl config.yaml

Make sure you have the right authentication for all three bucket types,
as is detailed in the docs.

Note that the JSON dump at the end still reports that the files are
stored locally, which is something that should be changed eventually
when using the --destBucket option.

BD2KGenomics/slugflow,BD2KGenomics/slugflow