Integrate legacy documentation

[kotfu]

Closes #722. When reviewing this PR, please don't review the content for accuracy. I've simply moved existing content into the new structure. We've got plenty of work still remaining which will be addressed in other issues/PRs:

• write new content to cover undocumented capabilities
• expand documentation on topics that are not fully described
• update/correct existing documentation which no longer accurately describes current functionality

[codecov]

Codecov Report

Merging #726 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #726   +/-   ##
=======================================
  Coverage   97.15%   97.15%           
=======================================
  Files          13       13           
  Lines        3371     3371           
=======================================
  Hits         3275     3275           
  Misses         96       96

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[tleonhardt]

I took a quick look through and everything looks good

[NekoShinobi]

Just out of curiosity, is there a way to see our branches on readthedocs? Or is there something preventing from that happening?

[kotfu]

We only push to readthedocs when we cut a release. However, you can easily view the documentation from any branch you have checked out in a web based format that looks exactly like readthedocs. From your checked out branch type:

 $ invoke livehtml

Then open your browser to http://localhost:8000. Your browser will show exactly what you would see in readthedocs.