deleted Eta example. One example is enough.Maybe I will ad it again later.
created file for pi0-example main.
added GHistMamager with GLinkedHist. Every linked hist will be saved automaticly in the end. There is an optional bool in the constructor of GLinkedHist to switch it of.
first idea of scaler corrected histogram.
further development on GScaCorHist
changed Pi0-example to test GScaCorHist.