message: added options portion  for  HDF5
diff: @@ -30,3 +30,13 @@ To read back the h5 files generated with VDS to ADIOS2, one can use the HDF5 eng
  The h5 file generated by ADIOS2 has two levels of groups: The top Group, ``/`` and its subgroups: ``Step0`` ... ``StepN``, where ``N`` is number of steps. All datasets belong to the subgroups.
  Any other h5 file can be read back to ADIOS as well. To be consistent, when reading back to ADIOS2, we assume a default Step0, and all datasets from the original h5 file belong to that subgroup. The full path of a dataset (from the original h5 file) is used when represented in ADIOS2.
  +
  +We can pass options to HDF5 API from ADIOS xml configuration. Currently we support CollectionIO (default false), and chunk specifications. The chunk specification uses space to seperate values, and by default, if a valid H5ChunkDim exists, it applies to all variables, unless H5ChunkVar is specified. Examples:
  +
  +.. code-block:: xml
  +
  +<parameter key="H5CollectiveMPIO" value="yes"/>
  +<parameter key="H5ChunkDim" value="200 200"/>
  +<parameter key="H5ChunkVar" value="VarName1 VarName2"/>
  +
  +We suggest to read HDF5 documentation before appling these options.
  