MPI operators

Closes #42, #43, and #45

See merge request !16

fix examples times_of_interest, fix graph builder io_params, fix useless folder generation, fix argparser io_parms, add hdf5_disable_slicing, set io_params=False by default

Merge branch 'mpi-operators' of gricad-gitlab.univ-grenoble-alpes.fr:particle_methods/hysop into mpi-operators