Make the setting of the sign of pT of Velo only tracks deterministic
Added code to set the pT of the VELO only tracks with a sign based on the first strip in the first cluster rather than the track key (which was random). Also an option to reverse the sign for mag up/mag down MC comparisons. (TrackTools/src/TrackStateInitTool, TrackUtils/src/TrackPrepareForFit, TrackUtils/src/TrackPrepareVelo)
See discussion in LHCBPS-1547
See merge request !85 (merged)