Install simplification

[SebastienRietteMTO]

At the beginning, it wasn't possible to use the official versions of AROME and Meso-NH to plug PHYEX because of the too many differences in the source code and in particular the changes in the source directory organisation.

Starting from cy49t1 for arome and v5.7 for Meso-NH, we could:

• use "official" pre-compiled pack for AROME (maybe through the same tools as those used by davaï)
• use official tar.gz for Meso-NH
• put Meso-NH test cases in a separate directory (like the conf_tests one used by AROME), except if all the tests are available in the official tar.gz file
• modify the testing.sh script to allow for automatic running of the reference versions when missing

This evolution needs some modifications in the check_commit_ial.sh and check_commit_mesonh.sh scripts and allows the suppression of the 'pack' subdirectory in the PHYEX repository. Documentation must also be updated.

Moreover, a limited set of testprogs data could be made available on a web page to ease the use of these test programs.

A small install script could be written to install filepp, mnh_expand and the testprogs data.

[SebastienRietteMTO]

0b8e579 adds automatic running of the reference version for arome model

[SebastienRietteMTO]

2cea52c adds automatic running of the reference version for mesonh model