* mln/core/concept/check.hpp,
* mln/core/concept/image.hpp: Set check method in its own file.
* mln/core/concept/iterator.hpp: new style iterator concept
* mln/core/image/internal/nested_loop_iterator.hpp: New style iterator
* mln/core/iterator/iterator_base.hpp: Facade for iterators.
* mln/core/range/iterator_range.hpp: Util to build range from iterator.