Philippe 09/03/2018: IO/LFI: add NFILENAMELGTMAXLFI parameter and use it to force size in LFI file of MY_NAME and DAD_NAME
This is done for backward compatibility.

If truncated with TRIM/LEN_TRIM => problems with conv2dia

Philippe 06/02/2018: IO: modify NGRID for several fields (to remove problems with PARIS_GARDEN testcase)

Philippe 29/01/2018: FIND_FIELD_ID_FROM_MNHNAME: add optional argument ONOWARNING to remove warning messages when they are normal (debug level)

 Conflicts:
	src/MNH/diag.f90

+ correction for DMFCONV attributes

Philippe 25/01/2018: IO: _FillValue cannot be modified (or re-written) if some data has already been written

* add latitude(_x) and longitude(_x) fields in NC4 files
* set the coordinates attributes for fields
* commented out CSTDNAME for LAT and LON fields to not have 2 times the same standard_name
* corrected NGRID for DX/YHAT fields
* modify condition to detect if program is PREP_SURFEX

Philippe 23/01/2018: IO: add support for Arakawa uvw point in NC4 files (probably not used but set for completeness and future use)
+ small improvement for uw and vw points (more adequate choice of coordinates)