Add norm method on Position
Add norm method on Position

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