Create the Fortran documentation using standard tools

[zaikunzhang]

It is necessary to creat the documentation for the Fortran version of PRIMA using standard tools, e.g., FORD or Sphinx. Hugo seems also a very good choice (does it support Fortran)?

We must take other languages into consideration. The documentation for different languages should be consistent in terms of both content and style.

Finally, all documentation should be available under libprima.net.