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 implemented bestTrack for the new btag fwk, it was our own implementation and we realized that normalizedChi2, being an approx integer, can be zero even for genuine tracks in miniaod.
On the other hand packedHits is always non zero when the track information is available.