Readability edits in Meshes/

src/TNL/Meshes/DummyMesh.h

src/TNL/Meshes/Mesh.h

src/TNL/Meshes/MeshConfigBase.h

src/TNL/Meshes/MeshDetails/MeshEntityReferenceOrientation.h

src/TNL/Meshes/MeshDetails/MeshEntity_impl.h

src/TNL/Meshes/MeshDetails/layers/CMakeLists.txt

src/TNL/Meshes/MeshDetails/layers/MeshStorageLayer.h

...TNL/Meshes/MeshDetails/layers/MeshSubentityStorageLayer.h

src/TNL/Meshes/MeshDetails/layers/MeshSuperentityAccess.h

src/TNL/Meshes/MeshDetails/layers/MeshSuperentityAccessor.h

...L/Meshes/MeshDetails/layers/MeshSuperentityStorageLayer.h

src/TNL/Meshes/MeshDetails/traits/MeshTraits.h

src/TNL/Meshes/MeshEntity.h