Jupyter-instructortools

* **DEPRECATION**: Switched hide code to default Jupyter Lab collapse code
behavior.
* Added commands and menu items to undo the highlighted indication of
protected cells and those flagged for code-collapse or hiding on print.
* Added commands to allow temporary complete hiding (not collapse) of code
but not the output.
* Console debug messages off by default.

* Converted to a Jupyter Lab 4+ and notebook 7+ compatible plugin.
* Updated dependencies to be Jupyter Lab 4+ and notebook 7+ compatible.
* Switched to Jupyter compatible BSD license.
* **DEPRECATION:** Support for classic Jupyter (nbclassic) is dropped.
Versions 0.6.1 should still work with classic Jupyter.
* Added capability to enable and disable the Instructor Tools menu as well
as show and hide it using the Jupyter Lab command palette. This allows the
plugin to exist in a Jupyter Hub
installation used by both the instructor and students. By default, the menu
is deactivated and will not activate if a student has a notebook set to
disallow use of instructor tools.
* Added boilerplate instructions for creating a pdf of notebook with
collapsed headings.

0.6.1
* Updates to requirements to utilize upstream bug fixes.
0.6.0
* Converted to hierarchical menu that appears in the menu bar rather
than the toolbar.

* Simplified styling of highlight bars to reduce chances of markdown
cell sanitization making them not show up.
* Converted highlights to look more like brackets.
* Added option for a red left bracket highlight.
* require notebook version >= 6.4.10 for security fix.

* require notebook version >=6.4.7 for html styling and security
fixes.

* Expanded highlight bar options to insert in markdown cells to:
horizontal green start; horizontal brown stop; left vertical
chrome-blue highlight (only works well in Chrome browser).
* Pin the notebook version to 6.4.0 because 6.4.1+ has started
stripping all html styling from markdown cells.

* Added option to flag cells as hide_code_on_print.
* Added option to flag cells as hide_code (auto-hidden in
JPSL).
* Added ability to highlight these cells.