Handle LHE only generation in logParser and CI

I just tried to commit a few JOs for LHE-only production using Gen_tf. It seems that the logParser doesn't really recognise this, as it complaints about many things related to the shower.

Can the checks below be removed if outputTXT is used? This said I feel I have encountered a large enough number of issue by trying to produce only LHE events, that I am not sure this will be a very useful/used feature.

cheers, Simone

ERROR: generatorTune is missing! Failed tests: ERROR: TestHepMC Events passed is missing! ERROR: TestHepMC Efficiency is missing! WARNING: SimTimeEstimate RUN INFORMATION is missing!

• Total no. of events: 1 <-- WARNING: This total is low enough that the mu profile may be problematic - INFORM MC PROD

Logs in /afs/cern.ch/user/a/amoroso/public/PowhegEWintegrations/600001