Refactoring the grids.

TODO

examples/heat-equation/tnl-heat-equation-eoc.h

examples/heat-equation/tnl-heat-equation.h

src/core/arrays/tnlArray.h

src/core/arrays/tnlArray_impl.h

src/core/arrays/tnlSharedArray.h

src/core/arrays/tnlSharedArray_impl.h

src/core/cuda/reduction-operations.h

src/core/tnlStaticFor.h

src/functors/tnlFunctionDiscretizer_impl.h

src/matrices/tnlMatrixSetter.h

src/matrices/tnlMatrixSetter_impl.h

src/matrices/tnlMultidiagonalMatrixSetter_impl.h

src/mesh/grids/CMakeLists.txt

src/mesh/grids/tnlBoundaryGridEntityChecker.h

src/mesh/grids/tnlGrid1D.h

src/mesh/grids/tnlGrid1D_impl.h

src/mesh/grids/tnlGrid2D.h

src/mesh/grids/tnlGrid2D_impl.h

src/mesh/grids/tnlGrid3D.h