Graph axes

This section demonstrates the axis subsystem of the graph module. The axes
delegate a lot of tasks to different components like ''painters'' (which
control how the baseline of the axis, the ticks and the axis title are drawn),
''texters'' (which create the label strings written on the ticks), ''parters''
(short for partionioners, which take care of determining appropriate tick
positions along the axis, and ''raters'' (which adjust the number of ticks to
match the available size).

In the present section, we will explain various basic aspects of these
components. Most of the time, the examples will not show a complete graph but
just a single axis. In that case, we will take an axis created along an
arbitrary path, partially in order to demonstrate the flexibility of PyX's axis
system but also too increase the coolness factor. Of course, in a real-world
example, you will use the shown features mostly for simple, boring, straight
axes.
