[GeoLib] Describe of purpose of file TestGrid.cpp.
Fix memory leaks.
[GeoLib::Grid] Shorten lines -> code more readable.
[GeoLib::Grid] Using std::array instead of "C" array.
[GeoLib::Grid] Rewrote initialization of grid data structures.
[MeshLib] Fix warning in test.
[GeoLib::Grid] Test for case x==const.