Support for running a workflow test without an ini file

- For example, if an ini file and parameters are not specified in the test json, the workflow test will be run with the workflow's default parameters
- In the case where the ini file is not specified, an "id" should be set, and the metrics file should be name <id>.metrics.  Override this be specifying "metrics_file" (either full path, or the file name in "output_metrics_dir").