Adding tighter skimming to MUON5
This MR adds a tighter skimming to MUON5, as discussed in https://its.cern.ch/jira/browse/ATLASEG-321
The idea is to apply a Zmumu/Zee/ttbar emu skimming for data, while running on MC unksimmed.
Also, matchiChi2 variable is added to the format for SMT studies.