Add tools to recalculate track weights in PVs

This is a partial fix to the Turbo PV refitting issue by enabling PV track removal on mdsts.

I've added:

• RefitVeloTracksAlg to extract VELO LHCbIDs from tracks and make VELO tracks (I couldn't find an existing algo to do this).
• RecalcLSAdaptPV3DFitterWeightsAlg to recalculate the track weights as used by LSAdaptPV3DFitter and add the tracks to PV's track lists.
• A python module to correctly configure the track and PV locations for each year.

@ibelyaev - I had to slightly modify LoKi::PVReFitter so it counts the number of tracks in the PV from (nDoF+3)/2 rather than the size of its track vector, so it can do the track removal when most of the tracks are missing. If a refit is triggered, it uses the size of the track vector, so I believe this shouldn't change anything otherwise.

@erodrigu - I've put this in Phys/VertexFit but maybe there's a more suitable home for it.

@apearce - I can still only get this to work on 2018 real data, otherwise I can't find the VELO clusters.

@cattanem - As mentioned at PAC.