add the label for PairProduction, HadronicInteraction and isDecay in PrChecker2

Three variables are added in PrChecker2 to label whether the track is originating from a decay, from a hadronic interaction or from a gamma->ee pair production. It might be useful if one would like to study the reconstruction performance of tracks from a decay or from the material interactions.

The log file and xml file of "make test" are attached: Test.xml Test.log

The modification is validated by using PrCheckerEfficiencyPlots.py to generate the kinematic distributions of tracks. The output histograms can be found in lxplus: /afs/cern.ch/user/m/mengzhen/public/Electron_Efficiency/tuples/spectra. As expected, no electrons are fromHI (from Hadronic Interaction), and no non-electron tracks are from PairProduction.