GeoModelUtilities: Add version of GeoVisitVolumes that doesn't track transforms.

Add a version of GeoVisitVolumes that does not track the transformations. GeoVisitVolumes was introduced as a way of avoiding the N^2 behavior of getChildVol(). But sometimes you care only about the list of volumes and not about the transforms, and GeoVisitVolumes was overkill for that since it also tracked the transforms. Add an alternate, faster, version that does not supply the transforms.