Define some kind of IO to work with besides minimal Fortran scripts

[fedebenelli]

While the library has reached a mature enough API to be straightforward to work with using minimal Fortran scripts (running them with fpm) a good IO with input files can be helpful to provide also sharable executable(s) that do reestablished calculations.

My first thought is to use some standard like json since it makes more sense to use a preestablished format that can also provide some interoperability between programs. Other alternatives are using a scriptable and embeddable language like lua that could give more flexibility.

The ultimate input file will probably be using the Python interface already being worked on its branch.