Moved the List class into the Containers namespace

src/TNL/CMakeLists.txt

src/TNL/Config/ConfigDescription.cpp

src/TNL/Config/ConfigDescription.h

src/TNL/Config/ConfigEntry.h

src/TNL/Config/ConfigEntryList.h

src/TNL/Config/ConfigEntryType.h

src/TNL/Config/ParameterContainer.cpp

src/TNL/Config/ParameterContainer.h

src/TNL/Containers/CMakeLists.txt

src/TNL/Containers/List.h

src/TNL/Containers/List_impl.h

src/TNL/Curve.h

src/TNL/Images/DicomSeries.h

src/TNL/Images/DicomSeries_impl.h

src/TNL/Matrices/MatrixReader_impl.h

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

src/TNL/Object.cpp

src/TNL/Object.h

src/TNL/Solvers/MeshTypeResolver.h

src/TNL/Solvers/MeshTypeResolver_impl.h