MET uncertainties in pat::MET
- add lines to the CFG to use PAT tools to compute shifted METs
- add datamembers for storing uncertainties into the pat::MET
- add EDProducer to do the packaging of that
- fix PAT tool that removes MC matching to only affect PATJetProducers
Also:
- by default rekey jet daughters
- add class version to packed candidates
we can have more METs, e.g. if running the MET Uncertainty tool
put a meaningful global tag