Better handling of huge tableau

Currently, all tableau of coefficients are *hard-coded* in the sources. This has at least 2 cons:

1. really error-prone with very bad visualization due to the 132 characters limit;
2. not flexible: add/modify tableau require touch the sources.

I think it is much better to read tableau from a separate file at run-time. I like to encode them in JSON by means of [json-fortran](https://github.com/jacobwilliams/json-fortran). However the big question is

> where place the *default* tableau files?

@zbeekman (@rouson @cmacmackin @jacobwilliams and all having a system-knowledge) Maybe I have already asked an opinion about this, but I do not remember your answer.

Do you know if there is some *standard* (or almost standard) place where unix-like libraries search for their *auxiliary-include* files read at run-time?

In the case a user do not want to perform a full-installation, but want to use sources (as often happens in our Fortran ecosystem) where should we search for such files? Maybe we need an **include** directory in the root project...

### Note

Some coefficients are well defined integer fractions, it can be very useful to add [FortranParser](https://github.com/jacopo-chevallard/FortranParser) as third party library for parsing tableau with such a coefficients definition.