adding option to use fake vertices, off by default
default value for useFakeVertices for backwards compatibility
getByToken migration: Muon-Seeded seeders of iterative tracking
getByToken migration: MeasurementTrackerEventProducer
Fixed thread-safety issues with ElectronLikelihood

Fixed const correctness problems with object directly and indirectly
held by ElectronLikelihood. Then enforced that only const functions
of the direct and indirect objects are called from const member functions
of ElectronLikelihood. This guarantees thread-safety.
Thread safety issues

Mark mutable so static analyzer knows it is protected
by atomic.  Fix thread safety issue in the copy constructor.
Use default memory behavior in the atomic functions.
setNewRun() and setNewLumi() should work always
AnalysisAlgos consumes migration.
TQAF remaining consumes migration.
CommonTools remaining consumes migration.
METFilters consumes migration.
JetMCAlgos consumes migration.
CommonTools complete remaining consumes migration.
Merge pull request #2797 from olivito/fakevtx_trkreg

RecoTracker/TkTrackingRegions -- option to use fake vertex in GlobalTrackingRegionWithVerticesProducer
Merge pull request #2814 from Dr15Jones/makeElectronLikelihoodThreadSafe

RecoEgamma/ElectronIdentification -- Fixed thread-safety issues with ElectronLikelihood
Merge pull request #2805 from gpetruc/getByToken-MeasurementTrackerEventProducer-MuonSeededSeeders-on710p4

RecoTracker -- getByToken: Muon-seeded seeding, MeasurementTrackerEvent
Merge pull request #2816 from wddgit/eventSetupThreadSafety1

MagneticField/Engine -- Thread safety issues
Merge pull request #2836 from vadler/71X-consumesMigrationV

AT consumes migration -- 71X consumes migration V
Merge pull request #2834 from wmtan/setNewRunMustWork

FWCore/Sources -- setNewRun() and setNewLumi() should work always
Merge remote branch 'origin/CMSSW_7_1_X' into CMSSW_7_0_X