feature: Add png for jupyter nb and saving (#382)

* feature: Add png for jupyter nb and saving

* feature: Add save to all plotters

* feature: Add end_task

Allow to programmatically do something after the loop is done.
F.ex save the plot.

* docs: Add save example, use faster refresh rate

The default was 1 second, but I think aiming for 100hz, and using
that as default is a bit closer to reality.

Then in the examples we can just use the default which makes for
less typing for the users!

* fix: Use better variable name, clarify docstring