Tracking vertex fix

Added the SimVertexs and refs to HepMC::GenVertexs to TrackingVertex in TrackingTruthAccumulator.cc and introduced two parameters in the trackingTruthProducer_cfi.py file, my changes are summarized in the last commit 35583bf. I also documented my changes in the source file, if they are insufficient please don't hesitate to send me an e-mail, also see my post in the Tracking hn.

The deletion of SimTracker/TrackHistory/plugins/TrackCategoriesAnalyzer.cc is more of an accident, I modified it to test my changes to the other files with it and removed it from the staging area in git so these changes will not be pushed; so if possible, please ignore this.
sorry I was not precise. I meant
vertexDistanceCut2_(vertexDistanceCut*vertexDistanceCut)
and 
if (distance2 < vertexDistanceCut2_)