Data format change in 710p7: having mva() and mva_e_pi() as GsfElectron::MVAOutput members

These changes aims at recording the mva for isolated and non isolated (ged)gsfelectrons. In particular this means that mva() is now the contained of the isolated electron mva and mva_e_pi() the container for the soft electron mva output. To make this clean, the estimation of the both mva() and mva_e_pi() is done in GsfElectronAlgos.cc. I had to add a new constructor to the (old) isolated mva estimator so that it can be called from GsfElectronsAlgos and at the same time compatible with other existing calls. Notethat now in PFEGammaFilters, the comparison with the minimal mva values is done with electron.mva() and electron.mva_e_pi(), but the filtering process does not change.