fix circular dependency between Node and Mesh

Cross compiling for Windows with MXE

change std::vector<MeshLib::Element const*> to std::vector<MeshLib::Element*>

Add Eigen sparse solvers

Final cleanup

Reduces number of implicit type narrows.

Wrong parameter names.
Empty statements.
Unify comment style. /* */ vs ///

Tclap as a submodule

- Raised minimum CMake to 3.1 because of better crosscompiling support
  and imported target feature
- When Eigen is not found it gets downloaded before BaseLib is build
- Silenced OpenMP CMake output

Executables can be run with Wine.

Test and NumConfig for EigenSolvers.

Removed using namespace GeoLib.

fix includes in MeshLib and MeshGeoToolsLib