Limit latex equations to page width.
Fixed latex template to support multicol w/ adjustbox.
add page-up and page-down functionality to the autocomplete dropdown
correction in widget.js
one more bit
test: changing text of cell resets rendered status
Partial updates of css and visible + simplification of widget_container
changing the text should reset rendered flag
widget simplification continued
widget changes continued
correction
move some responsive bootstrap transitions

- `-md-` puts the transition at 970px
- `-sm-` puts the transition at 768px

I moved most of the `md` transitions to `sm`,
which seems more reasonable.
I also moved the cluster list to `xs` because
the columns will never be wider than a dozen or so characters.
Introduce info/warning/danger to notification area

Add corresponding style.

Should fix #5984

Error when (auto)saving and things along should stand out in the
UI for the user to investigate the reason as soon as possible not to
loose work later.
Allow switching kernel from the notebook UI
Change displayed kernel name when our session is started
Style kernel name
Line dropdown up on RHS of kernel name
Store kernelspec in notebook metadata on change
Start kernel according to loaded notebook metadata
Add method to change codemirror mode of all code cells