Added warning message for S(a,b) table renaming
Added warning message for S(a,b) table renaming

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