Combined the elemental and material calculate_xs routines
Combined the elemental and material calculate_xs routines

mit-crpg/openmc,walshjon/openmc,shikhar413/openmc,liangjg/openmc,liangjg/openmc,mit-crpg/openmc,walshjon/openmc,johnnyliu27/openmc,wbinventor/openmc,smharper/openmc,shikhar413/openmc,wbinventor/openmc,amandalund/openmc,smharper/openmc,walshjon/openmc,wbinventor/openmc,johnnyliu27/openmc,amandalund/openmc,paulromano/openmc,shikhar413/openmc,liangjg/openmc,bhermanmit/openmc,bhermanmit/openmc,shikhar413/openmc,smharper/openmc,johnnyliu27/openmc,smharper/openmc,paulromano/openmc,wbinventor/openmc,amandalund/openmc,paulromano/openmc,amandalund/openmc,mit-crpg/openmc,walshjon/openmc,paulromano/openmc,mit-crpg/openmc,liangjg/openmc,johnnyliu27/openmc