collapse parts of a html notebook

[jankatins]

I do my data analysis in a notebook and the notebook starts to become too big to be useable.

It would be nice if one could collapse certain parts of te notebook, so that only the parts where one is working right now are visible in the browser. Something like "sections".

[Carreau]

The output should be collapsible to gain place.
The notebook format does support worksheet, we just didn't had time to do it in the UI.

[jankatins]

It would already be nice to include https://github.com/danielstocks/jQuery-Collapse/ and letting it collapse everything between (manually included) headings.

[jankatins]

after finding #805 this seems to be a duplicate: closing and adding the last comment to the other bugreport.