Flowserv-core

* Allow user-defined workflow and group identifier (\59).
* Merge `flowserv` and `flowapp` console scripts.
* User-defined keys for output files (\60).
* Add functionality for asynchronous runs to flowserv application object.
* Change flowserv application run result object (\61).
* Configure authentication policy via environment variables.
* Create separate groups for each workflow run in the app (\62).
* RunResults `get_file` returns a single file object (\63).
* Flowserv class for running workflows in notebook environments (\64, \65).

* Refactor code to include abstract file store for alternative storage backends (\54).
* Implement file store for S3 buckets.
* Avoid redundant storage of static files for workflow runs (\55).
* Remove old workflow runs from database (\9).

* Handle optional manifest element in workflow repository entries (\52).

* Allow Conditional Parameter Replacements (\50).

* Commit changes after run state update (issue \48).

* Option to add specification of output file properties for display purposes in workflow specification.
* Rename data type element in parameter declarations and result schema columns to 'dtype'.
* Add manifest file option as parameter for test workflow runs in Jupyter.
* Test workflow runs using Docker engine.