* Ferret: Add missing dependency with curl.
* Ferret: Don't force using the static version of libgfortran.
* Ferret: Ensure Spack's compiler wrappers are used.
This allows properly setting the rpaths.
* Ferret: Add support for versions 7.3 to 7.6.
* Ferret: Add a variant to install Ferret standard datasets.
* Ferret: Define some useful runtime environnement variables.
* Ferret: Fix flake8.
Also add myself as a maintainer as suggested by @alalazo.
ccb316964d