Modify Radial Distance Utils to Work With Both Sub Classes of MagnetSet()

[Edgar-21]

As noted in #182, the only thing the coil filament data is used for in MagnetSetFromGeometry() is so the radial distance utilities work with both subclasses. Removing the coil filament data from MagnetSetFromGeometry() and updating the radial distance utilities so it will work with both subclasses seems to make sense from a separation of concerns point of view.