autoscale the view when replotting

[ltalirz]

form the MARVEL Site visit in April 2018:

when editing the view, replotting does not seem to reset the view (and thus the newly plotted points may not be shown)

[ltalirz]

Besides trying to add the adjustments by hand, the reset tool can be triggered via javascript.

It is currently not possible to call JS from python directly but it can be done by attaching callback to a source that changes.

Problem is: you can't attach both a python call and a CustomJS to a callback at the same time...