Removed Cel.fill property in place of Cell.fill_type
Removed Cel.fill property in place of Cell.fill_type

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