decl_hdf5 MPI-I/O Collective or Independent, fix #419

[jmorice91]

Possibility to choose parallel MPIIO pointer (COLLECTIVE/INDEPENDENT) for hdf5 in parallel.

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[jmorice91]

Previous review are in #494

[JAuriac]

OK.
Three minor comments to change.

[Yushan-Wang]

Good to go!

[benoitmartin88]

LGTM