enhance IEs with more control over Galaxy

spawned from [twitter](https://twitter.com/ctitusbrown/status/922523301599100928)

would include e.g. submission, status querying, and retrieving results

I can imagine something like `submit(workflow_uuid)`, `status(workflow_uuid)`, `results_for(workflow_uuid)`

The issue proposes Galaxy interface operations for submitting workflows, querying status, and retrieving results by workflow_uuid, but names no files or tests. Start by locating the existing IE implementation and its workflow entry points. Done would mean these three operations are defined and usable with a workflow_uuid, with coverage for submission, status, and result retrieval.

Written by the indexing model from the issue text.