add pileupjetid and tree code for pileupjetid validation

I don't know how 'CMSSW-style' we want to be for the microAOD producers, but in my understanding cout is not so well-behaved with respect to threads and we should use the MessageLogger from CMSSW instead [1] ?

For the commissioning code I guess this is ok since it runs on microAOD / interactively.

[1] https://twiki.cern.ch/twiki/bin/view/CMSPublic/SWGuideMessageLogger