Base fragment triggering single core if needed
The software coordinators asked Physics Modeling conveners to try to run all Madgraph/aMC@NLO jobs in the production system using multicore. Technically this should be not difficult and the ProdSys expert is looking into the possibility to switch to multicore mode based on the jO name.
However if we do this we need to make sure that we switch to single core mode before Pythia8 is running. Obviously this could be done in the jO, but that's not reliable in general.
This MR puts this into the Pythia8_i Base Fragment.