Merge arome rain_ice with:
- Ryad's versio: optimisation, KPROMA blocs
- Meso-NH version: subgrid precipiation
Arome aux:
- mode_ll to provide get_indice_ll
- mode_budget

Known issues:
- Bug around KPROMA blocs: results are different when used
- precipitation fraction cannot be used as long as condensation is not merged
- mode_ice4_sedimentation_momentum is still not plugged

merge AROME, Meso-NH and Ryad's version
cleaning of forgotten modi
tools.f90 added from Meso-NH package

- mv *.f90 *.F90
- bug corrections in bl89 and compute_bl89_ml
- code modification to take into account the new interface of
bl89 and compute_bl89_ml
- introduction of the REPRO48 compilation key

Creation of the temporary 'externals' directory for AROME.
This directory will contain the AROME specific version of
source codes that is not part of the PHYEX package but is
needed by the package.

Main mods:
- XRTM17, LOCEAN and ocean related constants added
- AROME specific version of modd_precision, modd_dynn created
- creation of a message system for AROME: modd_io and mode_msg

Other mods:
- mv budget in externals
- creation of the docs directory (containing working documents)
- creation of src/arome/gmkpack_ignored_files; the file contains
  the list of the source codes which must be ignored by gmkpack
  but was present in the main pack. This file is necessary while
  the ecboundle mechanism is not used.