3D: Support plotting of axes
3D: Update example notebook
3D: Add lines to bound the faces
Color the axes for now.

As plotting fonts is a little more involved, we just color the axes for
now.
3D: Introduce per-plot identifier
3D: Hash the 3D vertices properly
3D: Add option to only plot points on the hull

Plotting less points makes the set faster to print and to illustrate
(e.g. when the user turns it)
3D: No need to hash, just make it a tuple

Hashing still caused troubles in case of hash conflicts. However, we can
use tuples without problems as indices in a map. The map will then do
the conflict resolution automatically.
Add function to compute a rectangular hull
Plot iteration space domain and related information
Allow to specify the edge style used when plotting a map
Allow to specify the edge width used when plotting a map
Add support to plot in a different space
plotter: Ignore divs when plotting the tile shape itself
Do not show vertices in plot_map_as_groups
support: Add sort_point

This sorts a list of points according to their lexicographic order.