Florent D'Halluin authored Sep 28, 2009 and Guillaume Lazzara committed Jun 15, 2010

* viewer/help_dialog.cc:
Update help message.

* viewer/image_view.cc,
* viewer/image_view.hh,
* viewer/image_widget.cc,
* viewer/image_widget.hh,
* viewer/viewer.cc,
* viewer/viewer.hh:
Update colors.  Improve cache usage (disabled when zoomed in).