Documentation should be unified and fuzzy searchable

[asonolet]

Today there is 3 to 4 documentations for MEDCoupling. This leads to some not being up to date, and the users being lost.

The mainly used documentation is the so called developer documentation, which regroups a broad documentation of MEDCoupling, and the API Doc. This doc is generated by doxygen. Doxygen is an amazing tool in its capacity to parse C++ code doc, but the html renderer is a bit outdated and the search function is not fuzzy matching. The other documentations are sphinx compiled with the classical theme ReadTheDocs - which is great and offers fuzzy matching search - , but their content is a bit outdated or duplicated relatively to the doxygen doc.

A proposed solution is to use breathe alongside sphinx to parse the xml output of doxygen in order to bring the best of sphinx and Doxygen together.