Develop jupyter directive for full control option

[mmcky]

Develop a custom Jupyter directive for sphinx that allows for full control of the notebook concept.

An example would be:

.. jupyter:: {{ language }}
    :type: in
    :no-execute:
    :label: xyz

or

.. jupyter:: {{ language }}
    :type: out
    :label: xyz

Potential to add:

• test support for checking output

the downside of using a custom directive would be support for other output types such as html and pdf.

[mmcky]

PR #84 starts this work to include a new directive to get more control over the jupyter notebooks, including the option of cell-break (e.g., when the text is too long)

Implemented:

• [x] :cell-break: break jupyter input cells
• [ ] :slides: include the option of each cell being a different sub-slide type. Enabling slides should probably be done at the project level in conf.py and the directive gives you control over type of slide. This option should only be available if a global slides option has been selected.

allow for explicit control of jupyter blocks

• [ ] :type: output, markdown, code

Notes

1. markdown and raw can have cell attachments https://nbformat.readthedocs.io/en/latest/format_description.html#cell-attachments