Image Buttons
-  Modify the class idvi.split.NavigationPanel to use an ImageButton class
	for the navigation buttons.  The current panel looks bad on a Macintosh
	because the button style is so different; ImageButtons would fix this.
	It is also unclear to many people that  + and - have to do with magnification,
	and the ? button doesn't jump out at people.  I want people to visit the help
	page and see the tips that are there!
	
 -  Design some good looking buttons.  Probably a Photoshop-style magnifying
	glass with + or - for the scale buttons, and buttons similar to the Netscape
	back and forward buttons for the page buttons.
	
 -  Figure out where to put the button images.  Probably the best thing is to
	store them as encoded strings in the NavigationPanel class, and write an
	ImageButton class which takes a string and decodes its image from the string.
	Otherwise we need to add image files to the distribution, and install them 
	somewhere, and find them from the applet -- too many things can go wrong.