Publish final outputs to persistent volume

[trey-stafford]

Currently, the simple recipes we've been experimenting with write all outputs to argo's artifact store. We are using this as an intermediate data storage solution that isolates the inputs/outputs of each step from each other.

Now we want to be able to write the final step's outputs to a persistent location that other workflows can reference.

Eventually the ogdc service may provide direct downloads of results from this location.

[trey-stafford]

Resolved by #50