Generalise trajectory fitting to consider 3D uncertainties in xyz #154
Description
Currently, only uncertainties in x&y are considered in the fit, but hits from panels that are not transverse will have uncertainties in z. Similarly, hits from panels at other angles will have uncertainties at angles to other hits. In order to generalise the panel definition, we need to generalise the track fitting to account for these "3D hyper-ellipsoid" uncertainties.