Add interface for linear sovlers. Add macros definition at global level. Adapt modules to test the different linear solvers.

Move Vector3d interface to tboxw.i. Replace Pt by Vector3d in heat, katropton, mirrors and sph + python files. Node.pos and Results remains

Merge remote-tracking branch 'origin/fix_msvc_build' into feature_eigen + remove commented line in CMakeLists

Added inlining for get methods in Element, Cache and Mem. Removed authorship in dox. Removed unused file.

Replaced std::vector by Eigen::Matrix in shape functions computations. Shape functions are now private and can be accessed by cache.get()

Replaced std::vector by std::deque to avoir size estimation when building list of triplet for sparse matrix