Delete volume and surface OBB trees

This PR addresses issue #77 . Functionality was added to Geom Topo Tool to delete the OBB tree of an individual surface or volume. This is needed in order to update the OBB trees of moving volume sets. When deleting the OBB tree of a volume, the user has the option to delete only the volume tree OR delete the volume tree and all of the OBB trees of the surfaces that compose the volume. This function will remove the OBB tree root from the Geom Topo Tool and Oriented Box Tree Tool data structures and delete the root entity set.