Added initial Tally arithmetic addition operation
Added initial Tally arithmetic addition operation

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