* doc/Doxyfile.in: Add IMAGE_PATH entry.

	* doc/Makefile.am: Add image dependency.

	* doc/about.dox: New.

	* doc/doc.bib: New reference.

	* doc/images/olena_layers.png,
	* doc/images/olena_layers.svg: New.

	* doc/mainpage.dox: Rename section.