NEW FEATURE: Implement an animate method

Summary

The Project class should get an animate method that creates an animation and saves it to disk

Reason

Because sometimes you only see your data when it is animated.

New behaviour

psy-view has this animation support (see https://github.com/psyplot/psy-view/issues/11) but it would be good to formalize this in psyplot a bit more to make it scriptable. This also requires some formality to prevent data-driven formatoptions (such as the bounds formatoption of the mapplot method, or the xlim and ylim formatoptions, to change constantly. Therefore, we need a

• psyplot.project.Project.animate method
• psyplot.plotter.Formatoption.prepare_for_animation and psyplot.plotter.Formatoption.stop_animation method