support energy cutoff in Python API
support energy cutoff in Python API

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