Edited NTupleStubs [3]

Also added nPV in NTupleGenEventInfo
Also added VarParsing to test_ntuple_cfg.py
Factorized NTupleStubs

Hence added NTupleSimTracks, NTupleSimVertices, NTupleSimBeamSpot, NTupleTrackingParticles and NTupleTrackingVertices
Merge branch 'feature-ntupletools'