Use m_cell_to_node_matrix outside of connectivities

src/mesh/Connectivity1D.hpp

src/mesh/Connectivity2D.hpp

src/mesh/Connectivity3D.hpp

src/mesh/GmshReader.cpp

src/mesh/Mesh.hpp

src/mesh/MeshData.hpp

src/mesh/MeshNodeBoundary.hpp

src/output/VTKWriter.hpp

src/scheme/AcousticSolver.hpp