Adding dagmc attribute to the settings class.
Adding dagmc attribute to the settings class.

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