fix write 2D char arrays in HDF5
fix write 2D char arrays in HDF5

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