Merge branch 'prepare_linearizer' into 'master'

Core/include/Acts/Vertexing/FullBilloirVertexFitter.hpp

Core/include/Acts/Vertexing/FullBilloirVertexFitter.ipp

Core/include/Acts/Vertexing/HelicalTrackLinearizer.hpp

Core/include/Acts/Vertexing/HelicalTrackLinearizer.ipp

Core/include/Acts/Vertexing/IterativeVertexFinder.hpp

Core/include/Acts/Vertexing/IterativeVertexFinder.ipp

Core/include/Acts/Vertexing/LinearizerConcept.hpp

Core/include/Acts/Vertexing/TrackToVertexIPEstimator.hpp

Core/include/Acts/Vertexing/TrackToVertexIPEstimator.ipp

Core/include/Acts/Vertexing/VertexFinderConcept.hpp

Core/include/Acts/Vertexing/VertexFitterConcept.hpp

Core/include/Acts/Vertexing/ZScanVertexFinder.hpp

Core/include/Acts/Vertexing/ZScanVertexFinder.ipp

Tests/Core/Vertexing/FullBilloirVertexFitterTests.cpp

Tests/Core/Vertexing/IterativeVertexFinderTests.cpp

Tests/Core/Vertexing/LinearizedTrackFactoryTests.cpp

Tests/Core/Vertexing/TrackToVertexIPEstimatorTests.cpp

Tests/Core/Vertexing/ZScanVertexFinderTests.cpp