Add new morphers.
	
	* tests/cast_image.cc: New.
	* tests/assign.cc: New.
	* tests/fimage.cc: New.
	* mln/core/fimage.hh: New.
	* mln/level/assign.hh: New.
	* mln/value/cast.hh: New.

	* mln/core/safe.hh: Rename as...
	* mln/core/safe_image.hh: ...this.
	* tests/safe_image.cc: Update.
	* mln/core/vec.hh: Rename as...
	* mln/metal/vec.hh: ...this.
	
	Handle constness in pixel iterators.
	
	* mln/core/internal/pixel_impl.hh (value_): New.
	(address): Update.
	* mln/core/internal/pixel_iterator_base.hh
	(qualified_value, value_): New.
	* mln/core/pixter2d_b.hh (value_): Update.
	* mln/core/dpoints_pixter.hh (value_): Update.
	* mln/core/internal/image_adaptor.hh
	(vset, values): Fix missing.
	* mln/core/concept/generalized_pixel.hh
	(ctor): Comment check on address.
	* mln/core/concept/pixel_iterator.hh
	(ctor): Comment check on lvalue and op*.
	* mln/core/concept/fast_image.hh (offset): Fix missing const.
	* mln/core/image2d_b.hh: Likewise.
	* mln/core/concept/doc/image.hh: Cosmetic changes.
	* mln/level/fast_median.hh (input): Update.

	* TODO: Update.


git-svn-id: https://svn.lrde.epita.fr/svn/oln/trunk@1034 4aad255d-cdde-0310-9447-f3009e2ae8c0