What is the best way to make a groupplot of a few groupplots?
I'll need to be able to add tick-labels to both "levels" (the inner and outer groupplots, think Inception 2010).
For example, each red/blue square is a plot. Each 5x5 pane is a groupplot of these plots. The whole thing is a groupplot of these 3x3 groupplots (this figure was done by generating PNGs for each of the 5x5 panes and inserting these with \addplot graphics to a single groupplot).
