Added SimVertex and refs to HepMC::GenVertex to TrackingVertex in 'createTrackingVertex'; for GenVertexRef used same approach from 'TrackingTruthProducer' in 5X so add all GenVertexs within a distance of 0.003 cm to TrackingVertex
Removed SimTracker/TrackHistory/ from tracking area
Different implementation of fix, now problem with 'PileUpEventPrincipal::getByLabel()' is already bypassed when calling 'TrackingTruthAccumulator::accumulate'; also 'vertexDistanceCut' and 'HepMCProductLabel' are added to SimGeneral/MixingModule/python/trackingTruthProducer_cfi.py as parameters
Added some more documentation
Update branch TrackingVertexFix
Summary of TrackingVertex fix:
	* in 'createTrackingVertex', add SimVertex to TrackingVertex which is created from the SimVertex ('returnValue.addG4Vertex(simVertex)')
	* also add ref to HepMC::GenVertexs in createTrackingVertex if it is a signal event; add all nearby GenVertexs (copied from old 'TrackingTruthProducer')
	* add handle to edm::HepMCProduct already in 'TrackingTruthAccumulator::accumulate' (and not in 'accumulateEvent') as 'event.getByLabel()' with it doesn't work with PileUpEventPrincipal
	* add parameter 'vertexDistanceCut' in SimGeneral/MixingModule/python/trackingTruthProducer_cfi.py to control this behaviour (set to 0.003 cm by default)
	* also add 'HepMCProductLabel' parameter in trackingTruthProducer_cfi.py
Restored .gitignore and SimTracker/TrackHistory/plugins/TrackCategoriesAnalyzer.cc plus a few changes in TrackingTruthAccumulator
Some minor changes
Updated trackingTruthProducerFastSim_cfi.py so that fastsim works as well
Modified trackingTruthProducerFastSim_cfi.py and trackingTruthProducerSelection_cfi.py to reduce overlaps between FastSim and FullSim
Merge pull request #4700 from dnowatsc/TrackingVertexFix

Tracking vertex fix