adding primary input dataset + PNN location into JDL

@ticoann @ericvaandering 
patch for PNN in JDL.
fixes issue #5340
Hi Eric,
This was the bit I was least sure of so I'm glad to have you review it. I understand I think. There is a similar WMTask method .inputDatasetPath() which returns /primary/processed/tier but I wasn't sure if that was what we wanted. from your comment it looks like this should be what I'm using so I'll straight swap them