Soline Bielli : 01/03/2019: Sea salt update: the significant sea wave height now influences salt emission.
The sea salt is either set to a default value of 2meters or read in ECMWF Grib file (if the variable exists).
Now 5 modes are available (3 before) and the order in output is changed.
The large-scale sea wave height from ECMWF grib is 2D. HALO2 update of the ls variable in modeln is not yet adapted to 2D field (it is switch off in this version for this variable).

Warning: not fully tested

+ removed some LEN=LEN_HREC for unrelated variables

+ removed unused variables

* modd_gridn.f90: all fields are now managed with TFIELDLIST
* added INI_FIELD_SCALARS subroutine
* corrected bugs for use of TFIELDLIST with all the PROGRAMS

Added fields: MY_NAME, DAD_NAME, DXRATIO, DYRATIO, XOR, YOR, WT

* added pointers to the data in TFIELDDATA type
 (via array of pointers (one per mesh))
* used the previous array of pointers for some fields
  -> modif of ini files for them
* added IO_WRITE_FIELDLIST subroutine to write
  a series of fields (i.e. provided for output)
* moved INI_FIELD_LIST from INITIO_ll to INIT_MNH
* added new fields to TFIELDLIST