New btag framework

First set of b-tag framework changes to allow b-tagging based on pf candidates as well as on tracks (standard approach).
Announced here: https://twiki.cern.ch/twiki/bin/viewauth/CMS/CMSSW_7_2_0
Presentation: https://indico.cern.ch/event/322860/session/1/contribution/18/material/slides/0.pdf
 
The plot attached shows the performance of the CSV tagger in 4 cases:
1) default: black circles -> performance of CSV before the framework changes
2) templated CSV: blue crosses -> performance of CSV after the framework changes using templates and tracks 
The performance is exactly the same for those two cases, which is what we want!
3) pf cands: red stars -> performance of CSV with pf candidates resulting 
-> proof that the new implementation works also on pf candidates
4) trk cands: green stars -> performance of CSV using track candidates 
-> recover of performance loss that we had compared to 3)
This was an attempt to do exactly what you are suggesting since right now this file sits in RecoBTag/SecondaryVertex/interface/ Moving it to DataFormats/BTauReco/interface/ also helped to avoid defining some commonly used functions (such as etaRel()) multiple times in several different places. Let us know of any alternative location where this file could be placed.