Moving towards release

[gwm17]

A lot of smaller changes centered around getting Spyral ready to release

• Switch to using black as the code format and format all files
• Switch to using numpydoc style in docstrings
• Generate documentation for the entire API, for use by developers
• Bump spyral-utils, remove explicit dependence on matplotlib from the code base
• Switch to plotly for all notebook plotting to better support interactivity
• Plotter is broken; replace with the particle_id.ipynb notebook -- plotter is scheduled for removal in future updates
• Update requirements.txt, add explicit dependence on jupyterlab
• Add more clustering parameters to the configuration, particularly for handling big vs. small point clouds

And some other small changes....

Nearly ready for release!