This MR adds the parametrised scatter concept to the
TrackMasterFitter. Certainly not the end-product, nor probably the place where this will continue on living.
Enabled by property
FastMaterialApproximation in TrackMasterFitter.
We should probably enable this by default in the Moore configuration, and regenerate quite a few references.
See https://indico.cern.ch/event/872902/contributions/3834670/attachments/2030645/3398400/200501_TF.pdf slide 5 to 9 for a description.