Windows compatibility

The compilation was broken on Windows. There was a problem in the SWIG-generated code from the new ELTYPE and MATTYPE class enums. More precisely, the problem was related to the translation of operator<< (which does not become print or __str__ but __lshift__ in python!). I have prevented SWIG from wrapping this function.
Compilation of Trilinos is automatically disabled on Windows since Trilinos is not compatible with Windows.

Compilation with old versions of gmm

It is now possible to compile the code with the (old) version of gmm that is bundled with Ubuntus<18. These old versions define std::operator<<(std::vector<double> const &) although the newest version does not. I previously added our own definition of this missing function in the header gmm_extra.h. Obviously, this definition broke the compatibility with the old version of gmm. Now, the TRY_COMPILE feature of CMake is used to check whether this function is already defined or not. This knowledge is transferred to the compiler using the new GMM_DEFINITIONS variable which is dynamically set in FindGMM.cmake (see this file for more details).

By default the new version of gmsh (version 4) writes meshes in a new (incompatible) format. I am currently trying to upgrade MshData so that it can read this new format. In the meantime, I have forced gmsh to write its output in version 2 (see gmsh.py). It temporarily solves the problem. We should, however, be careful to avoid gmsh4 commands in the .geo files!

I have added several basic .geofiles in mirrors. I will use them in a near future to make additional basic mechanical tests (to be continued).