Madgraph Wmunu production

As per request of @emmuhamm , I took a pass at trying to make the submission for the Madgraph NLO Wmunu production.

Unfortunately, at the stage of running the local test: lb-dirac dirac-production-request-run-local my_request.stage6.yaml I get some errors that I've been unable to bugfix.

I leave this here as I go on holidays, and maybe @emmuhamm or @lgiambas could have a look in the meantime?