New btag framework

[pvmulder]

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)

[cmsbuild]

-1

Tested at: 5b3677f
I ran the usual tests and I found errors in the following unit tests:

---> test runtestUtilAlgos had ERRORS

you can see the results of the tests here:
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-4694/600/summary.html

[Dr15Jones]

The test fails because of the xrootd change not because of this pull request.

[davidlange6]

by-passing AT signature as we'd like this in pre4 and there has been plenty of discussion already (complain if not ok)

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-4694/600/summary.html