Philippe 15/01/2021: bugfix: SV_FLUX for flyers were not computed correctly and overwritten in files

Philippe 14/01/2021: IO: add IO_Field_write_nc4_N4, IO_Field_partial_write_nc4_N2, IO_Field_partial_write_nc4_N3 and IO_Field_partial_write_nc4_N4 subroutines

-ZXCOEF and ZYCOEF were not computed if CVBALL
-PCIT was used if CCLOUD/=ICEx (not allocated)
-PSEA was always used even if not allocated (CSURF/=EXTE)
-do not use PMAP if cartesian domain

Revert "Quentin 11/12/2020: temporary force the possible uncorrected negative values to be > 0. This commit should be reverted soon and the missing right correction of negative values of rv must be found"

This reverts commit 582bf442.

-ZXCOEF and ZYCOEF were not computed if CVBALL
-PCIT was used if CCLOUD/=ICEx (not allocated)
-PSEA was always used even if not allocated (CSURF/=EXTE)
-do not use PMAP if cartesian domain

(cherry picked from commit d82def518a9d007cb8f8a827d7b872b774f4a965)

-ZXCOEF and ZYCOEF were not computed if CVBALL
-PCIT was used if CCLOUD/=ICEx (not allocated)
-PSEA was always used even if not allocated (CSURF/=EXTE)
-do not use PMAP if cartesian domain

(cherry picked from commit d82def518a9d007cb8f8a827d7b872b774f4a965)

Philippe 08/01/2021: allow output files with empty variable list (useful if IO_Field_user_write is not empty)

Philippe 07/01/2021: IO: remove GCLOSE_OUT variable/dummy argument (lopened field of tpfile datatype can be used instead)

This is incomplete for the moment. MesoNH must always be compiled with this key for the time being.

Philippe 06/01/2021: IO: add coordinates for dimension variables in diachronic files (not all yet done)

(cherry picked from commit 025cea89)

(cherry picked from commit 025cea89)

(cherry picked from commit fcebfc18)

(cherry picked from commit fcebfc18)

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