Add some tools related to morphers over image value.
	
	* oln/core/abstract/value.hh: New.
	* oln/morpher/thru_fun.hh: New.
	* oln/morpher/internal/image_value_morpher.hh: New.
	* oln/color: New.
	* oln/color/rgb.hh: New.
	* tests/Makefile.am (check_PROGRAMS): Reorganize.
	(io_pnm_SOURCES): New.
	* oln/core/abstract/grid.hh (grid): Add inheritance from oln::type.
	* oln/Makefile.am (nobase_oln_HEADERS): Update.



git-svn-id: https://svn.lrde.epita.fr/svn/oln/trunk@618 4aad255d-cdde-0310-9447-f3009e2ae8c0