Documentation overhaul

[jensens]

• fixes Consider splitting features of cookiecutter in README #721
• addresses Move docs to cookiecutter docs BruceEckel/HelloCookieCutter1#8 (removes submodule and links to repository)
• fixes Documentation 2.0: All tutorials should be combined to one menu #1411 (parts taken from stalled Combine doc tutorials to single menu #1423)
• addresses Documentation 2.0: CLI Commands documentation #1413 (moves cli docs to top level)
• addresses Document context injection #1613
• Remove debian installation instructions (part of Documentation 2.0: Meta task. #1409)
• fixes some Sphinx warnings
• doc style: one line per sentence (not everywhere yet). Hint: in case anyone wants to translate the docs in future.
• README indent and heading level fixes.
• several minor fixes.

[codeclimate]

Code Climate has analyzed commit f011240 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 100.0% (0% is the threshold).

This pull request will bring the total coverage in the repository to 100.0% (0.0% change).

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[ericof]

LGTM

[insspb]

@jensens thank you for contribution, but please do not do this in future:

doc style: one line per sentence (not everywhere yet). Hint: in case anyone wants to translate the docs in future.

Documentation translate make any project less maintainable (if it is not something with huge use), but such changes makes documentation in files harder to read.

@ericof Please consider my note in future documentation merges.

[jensens]

Documentation is not code, we did large documentations in the past with real experts on the topic.
One sentence per line is the standard.
So we should stick to it.

If you use Sphinx and may want to translate the docs in future (which may happen), then there is no way around this rule.
It is a question about inclusiveness, not about readability.

Nice side effects: Better readability on git diff after changes, easier to write (no manual newlines after inserting/removing words in a sentence and so on.

[insspb]

@jensens i do not remember any translation attempts. We do not have complete documentation in english. Nothing to say about other languages. But I remember moving to markdown #1216, and this will be done in future for most not auto-generated modules, as Myst support for rst is very elegant too.

About docs not a code. Docs for end users is much more required, but to develop a doc you need to look inside.
But did you tried to read 231 characters string on small screen? try, it will be fun.

Check pre-commit file history to find out how rst checks was set up in past. (2020) also check history of setup.cfg.

As for side effects etc... I cannot agree with it.

As is standart, For subtitles and things like that for sure. For docs? I see it first time. I do not know any maintainer, who want to watch and work with doc translation.