#8 Move the graphical output panel into a separate control

Currently, the output panel in the GUI is just a Panel, with
simple controls for how fast the output is animated. It would
be better to have this as a separate user control, and to add
support for play/pause/stop-style playback. This control could
then be used in other places, like the GTK graphical interface
or the viewer mentioned here: http://sourceforge.net/tracker/
index.php?
func=detail&aid=1223651&group_id=140347&atid=745927.