Bokeh continuous update - wip

[rafajak]

This PR tries to address the main comment in #57 :

• [ ] for drawing diagrams, don't clear_output(wait=True); it is possible to change a Bokeh blot in-place

So far, I managed to separate the figure-creating from plot-drawing, but at a cost of:

• general performance: everything appears much more sluggish, compared to the clear_output=True version in #57)
• the hover tool doesn't seem as reliable
• plot titles no longer want to show, for some reason.

This is very much work in progress and is not ready to be merged. Any help, suggestions or feedback on this would be much appreciated.

Raf

[stared]

@rafajak Thanks you for this PR

It refers to #19. I close PR #57 as it is about the same commits.

I would be grateful for a few things:

• screenshots in this PR thread
• rebase instead of merge (otherwise it may mess the history)