Arthur Crepin-Leblond authored Jul 16, 2010 and Guillaume Lazzara committed Nov 02, 2010

        * demo/viewer/browser_widget.cc,
        * demo/viewer/browser_widget.hh: Add arrows to change image and keep
        XML step.

        * demo/viewer/key_widget.cc,
        * demo/viewer/key_widget.hh: Change ListWidget to TreeWidget, Items can be
        disabled/enabled in groups.

        * demo/viewer/step_widget.cc,
        * demo/viewer/step_widget.hh: Small changes to keep the step when next/prev.
	picture is chosen.

        * demo/viewer/viewer.cc,
        * demo/viewer/xml_widget.cc: Layout adjustement.