Separate coil casing from winding pack

[connoramoreno]

For the magnet modeling, it would be valuable to separate, for each coil volume, the casing from the winding pack. This heterogeneity would give more accurate neutronics results, as the homogenization needed previously led to over-prediction of nuclear responses concerning the winding pack of the magnets, such as nuclear heating and fast neutron flux/fluence (no shielding from the casing). This separation should be included as an option in addition to the homogenized approach, if not used as the sole approach.