add new JER Flavour Composition config
- to apply analysis specific JER configurations for flavour composition, there needs to be the ability to apply the
AnalysisFile - this is an option for analyses looking to reduce the large jet flavour composition unc
- This is inline with the instructions on the jet/etmiss twiki: https://twiki.cern.ch/twiki/bin/view/AtlasProtected/JetUncertainties#DeriveFlavComp