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

Modifications prepared by Ryad are stored in arome/modset_Ryad
To help the merging of ice4_fast_ri, the array syntax was replaced
by a DO loop

gradient* files are merged and moved in externals
shuman moved in externals
modification of arguments order for shuman and gradients

rename rmc01.f90 into rmc01.F90

- 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

Quentin 08/11/2021: MNH->AROME tridiag* (Philippe 18/04/2019: import small improvements from OPENACC branch)

Quentin 05/11/2021: Merge MNH->AROME add RM17, LOCEAN, correction of exponent on final length for bl89, add MNHREAL