Philippe 17/12/2020: Write_time_coord: generalize to vector of dates and add management of date intervals (conform to CF conventions)

Philippe 15/12/2020: menu_diachro: more intelligent ygroup allocation (waste less memory + no more risk of access out of range)

Philippe 08/12/2020: budgets: modify group_name management (in order to merge different times in further commits for netCDF files)

Philippe 07/12/2020: add support for partial write of fields (optional argument: koffset, not all subroutines, no LFI spport)

Philippe 07/12/2020: add CLEANLIST1D_ll subroutine + use it to correctly deallocate associated memory

Philippe 07/12/2020: IO: add support for Z-split files in IO_Field_partial_write_nc4_X2 + create IO_Select_split_file subroutine

Philippe 26/11/2020: IO: remove dead code (compatibility of dates with old MNH, not working anymore)

Philippe 24/11/2020: rename NMNHDIM_BUDGET_MASK_TIME -> NMNHDIM_BUDGET_TIME and time_mask -> time_budget

Philippe 13/11/2020: IO: improve CF compliance (add missing unit, does not write empty standard_name)

Quentin 28/10/2020: default value of LRED is now TRUE (LRES = reduction of time dependency of ICE3/ICE4 microphysics scheme)

Quentin 27/10/2020: SURFEX v9, mis-usage of YRECFM (of size = LEN_HREC) variable for a comment variable. In SURFEX offline, LEN_HREC=12 which is not compatible here.

(cherry picked from commit f06a12ec)