more generic implementation of NjettinessAdder so it works with any jet type inheriting from reco::Jet
added LogWarning printout
further generalization for N's used in the tauN computation
Merge pull request #4664 from ferencek/NjettinessAdderMadeMoreGeneric_from-CMSSW_7_2_0_pre1

More generic implementation of NjettinessAdder