bugs

Histogram blows up when its data is removed
colors do not appear to be threading (11-03-08/plot-dists.pl)
legends
criss-crossing lines for high zoom levels (maybe need to change Prima
	interface to use double instead of int)

Colors
======
Switch to using Maggie's ColorSpace

Emphasizing Data
================
Teach DataSets how to emphasize and de-emphasize their data
Teach Palettes how to emphasize and de-emphasize their colors

Legends, Color Bars
===================
One legend entry per data set
Auto-detect features based on explicit DataSet properties
Zoom/pan on color bar emphasizes data in that color range

Grid/Matrix
===========
To speed up rendering, work with images
If grid bounds are within viewport, or extend just outside, use a single
	Image.
If grid bounds are much larger than viewport, work with tiles of Images that
   cover slightly beyond the current view.
 - Create function/method that updates the tiles one data-row or column at a
   time. This will preserve user interaction while still updating the plot
 - When panning (say) left, once the leftmost tiles pan far enough, simply
   move them to the far right.

On zoom, create first "image" of zoom based on a zoom-in of the current
	image or tiles. Then use the UI rendering method to improve resolution.
Might want to create a whole new Prima image class for this