Event variables and weights, imported from KrAFT

Event variables and weights are calculated and stored in flat format.

  * PDFWeightsProducer :  PDF reweighting factors including ones for systematic uncertainty
  * PileupWeightProducer :  pileup weights, also including syst. variations
  * RecoEventInfoProducer : Some reco level event info, nPV, pvX,Y,Z, HLT trigger results. HLT results are stored in simple integers, thus easy to ntuplize triggerResults.

Corresponding cfi files are also added.

Caveat
  * How can we make PDF reweighting to reserve absolute cross section in the workflow?
  * PU weight factors are from Run2012. consider as dummy for 7XY development for now.