Parametrised scatters (Ported from track-fit-workshop branch)

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.