Addition of TrackVectorFitter

This merge request should go together with LHCb!551 (merged) and Brunel!143 (merged).

Changes that affect TrackMasterFitter:

• TrackBestTrackCreator processes tracks in stages now.
• operator()(LHCb::Track&) and operator()(std::vector<std::reference_wrapper<LHCb::Track>>&) have been added to TrackFitter.
• Fixed a small bug in TrackMasterFitter by which the filter status of the first node was never reset upon updating transports.

Addition of TrackVectorFitter : public TrackFitter, that processes several tracks utilizing vector units:

• Options of TrackVectorFitter are for the most part the same as for TrackMasterFitter.
• Addition of package Tr/TrackVectorFit.
• In order to fully exploit the target machine, it should be compiled with make CMAKEFLAGS="-DGAUDI_ARCH=arch=native" configure.