added neighbor management, nEdges, nFaces

MeshLib/Elements/Edge.h

MeshLib/Elements/Element.cpp

MeshLib/Elements/Element.h

MeshLib/Elements/Face.h

MeshLib/Elements/Hex.cpp

MeshLib/Elements/Hex.h

MeshLib/Elements/Prism.cpp

MeshLib/Elements/Prism.h

MeshLib/Elements/Pyramid.cpp

MeshLib/Elements/Pyramid.h

MeshLib/Elements/Quad.cpp

MeshLib/Elements/Quad.h

MeshLib/Elements/Tet.cpp

MeshLib/Elements/Tet.h

MeshLib/Elements/Tri.cpp

MeshLib/Elements/Tri.h

MeshLib/FemMesh.h

MeshLib/FemNode.h

MeshLib/Mesh.cpp

MeshLib/Mesh.h