[MeL/IO] HDF: reduce data size

• Tests are in !3380 (merged)

• <compress_output>true</compress_output> in prj-file

• only variable attributes get written at each time step

• chunks can now be set independently of local size of data.

• HDF is kept open - this reduces numerous reads (performance)

Caution:

• When compression and consequently chunking is turned in on (<compress_output>true</compress_output> in prj-file) it is not possible to measure with Darshan. The error has been reported to HDF Group https://forum.hdfgroup.org/t/parallel-hdf5-write-with-irregular-size-in-one-dimension/8284 and to the Darshan mailing list and will hopefully be fixed soon.