updated MPI I/O interface to include writing/reading more types
updated MPI I/O interface to include writing/reading more types

liangjg/openmc,amandalund/openmc,mjlong/openmc,amandalund/openmc,kellyrowland/openmc,nhorelik/openmc,samuelshaner/openmc,shikhar413/openmc,wbinventor/openmc,sxds/opemmc,kellyrowland/openmc,wbinventor/openmc,samuelshaner/openmc,mjlong/openmc,shenqicang/openmc,shikhar413/openmc,lilulu/openmc,walshjon/openmc,paulromano/openmc,mit-crpg/openmc,paulromano/openmc,bhermanmit/openmc,paulromano/openmc,walshjon/openmc,sxds/opemmc,liangjg/openmc,mit-crpg/openmc,paulromano/openmc,amandalund/openmc,mit-crpg/openmc,shikhar413/openmc,smharper/openmc,amandalund/openmc,liangjg/openmc,lilulu/openmc,liangjg/openmc,walshjon/openmc,wbinventor/openmc,johnnyliu27/openmc,shikhar413/openmc,wbinventor/openmc,shenqicang/openmc,johnnyliu27/openmc,smharper/openmc,nhorelik/openmc,samuelshaner/openmc,johnnyliu27/openmc,bhermanmit/cdash,bhermanmit/openmc,walshjon/openmc,smharper/openmc,samuelshaner/openmc,smharper/openmc,mit-crpg/openmc,lilulu/openmc,johnnyliu27/openmc