Switch on BTag from candidates in reco and provide corresponding PAT tools

This PR runs one candidate based tagging (exploiting the new fwk) in RECO.
The corresponding code in jetTools.py (and related PAT stuff) is also added.

@ferencek @pvmulder
we figured that some neutrals (photons) could have attached tracks that are not of any help for b-tag.
further tuning of this selection is anyhow expected for 73X (actually it was for 72X but the cut of release schedule changed a bit our plans)