update tutorial notebooks and docs in prep for v2.0

[mperrin]

• Include the four tutorial notebooks using nbsphinx
• Update the doc toctree so the left hand nav bar looks better and functions better, in terms of organization and how the subsection details expand when you click onto a given page.
• Update the tutorial notebooks themselves.
  • Switch NIRCam contrasts to use F444W, for consistency with the NIRCam reduction notebook.
  • Update MIRI reduction notebook to use some of the enhancements and cleanup already applied to the NIRCam reductions notebook