Addition of metadata generation for planemo run

[Delphine-L]

Add the command --output_metadata FILE to planemo run. Generate a json file containing the workflow ID, invocation ID, and history ID created by the 'run' command.

[bernt-matthias]

Would it be possible to add a test? Maybe here: https://github.com/galaxyproject/planemo/blob/5a0eb3185a02f71f6312b680b67e8bf0deae7b8d/tests/test_run.py

[simonbray]

I think either --test_output_json or --output_json should provide this information already.

[Delphine-L]

I think either --test_output_json or --output_json should provide this information already.

You're right. The info is in --test_output_json. Thank you !