Revert "added NTracks for WC to tree. Needed to calc efficiency."

This reverts commit 827d3a5975f5efd57eea50883191f4c7d9be033c.
created file for pi0-example main.
created file for eta-example main.
moved Init functions to GConfigFile. No overloaded function needed in Physics class.
error checking in GTreeParticle::Particle, to avoid seg fault.
    added GHistMamager with GLinkedHist.
    Every linked hist will be saved automaticly in the end.
    There is an optional Bool_t in the constructor of GLinkedHist to switch it of.
added name of output directory as a member of GLinkedHist. Write has been overwriten, now the output dir will be created first in output file and hist is written to there.
renamed GLinkedHist to GHistLinked.
better handling of dir name in GHistLinked.
added GScaCorHist. This class provides automatic ScalerReadCorrections. It is derivated from GHistLinked.
renamed GScaCorHist to GHistScaCor.
OutputDirectories are working properly in GHistScaCor, even by copying and adding.
first idea of GHistBGSub. Only tested for no PR cuts.
GHistBGSub is working with 1 rand cut now.
GHistBGSub is working with multiple rand cuts now.
added GH1. Class will provide tagger binning in future. At the moment only a wrapper for GHistBGSub.
GH1 working now properly.
by default no ScalerCorrection Histograms produced. One can use kTRUE as second argument in ScalerReadCorrection to see the histograms.
added GH1-example for testing.