Disambiguate workflow engines by workflow_engine_name parameter

If WESkit supports multiple engines that support the same workflow type and workflow type version (e.g. for CWL), then just the workflow type and type version provided by the REST-API (according to standard) cannot unambiguously mapped to one engine.

To cope with this, the SAPPORO group introduced an additional workflow_engine_name run parameter, which, however, is not yet in the standard.

Note that multiple engines and engine versions may provide the same workflow type and version. This means, in principle, to fully specify which engine to use, the client would have to provide not only the workflow_engine_name but also the workflow_engine_version.