Adapt PF algorithm for high pT jet substructure

Change in PFAlgo to fix the jet mass reconstruction of highly boosted W bosons.
The PFAlgo creates merged photons and neutral hadrons from an excess of energy in ECAL and HCAL.
With this fix, these neutrals are split up into ECAL clusters to enable jet mass measurement.
The change is only applied to merged neutrals containing >=2 ECAL clusters with E>50 GeV and has therefore no effect on low energy reconstruction.

This change increases slightly the number of high momentum neutral particles in the event, but has no impact on jet energy fractions or jet energy scale/resolution. Only jet mass scale/resolution is improved.

Presentations at xPOG and JetMET
https://indico.cern.ch/event/320480/contribution/8
https://indico.cern.ch/event/322766/contribution/5

The XYZVector is not stored in a map, so one cannot store simply the keys of the ecalSatellites collection.
The std:pair from the ecalSatellites is push_backed into ecalClusters. Does this make a full copy of the XYZVector in the std:pair?
In order to simplify the code according to the other comments, in a special case a XYZVector not present in ecalSatellies is push_backed into ecalCluster.