History for distribution plots

[jpoeppel]

Distributions currently only show the current snapshot. It might be nice to save the history of distributions and be able to move back in time, to lock at how the distributions looked x-steps before?

[jpoeppel]

Main question is how to visualize the steps (ideally one would need something like a timeline under the plot where one can move back and forth).

Also how to handle the controls? Add buttons to figurePanel or to channel config? Just use hotkeys?