Review and update Configuration doc

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Introduce user and poly config as separate categories.

Include filename in section headings.

Group all deps.edn config section headings under a new section heading.

Explain how each config file is initially created and how it is changed.

Clearly mark derived configuration.

Show default config values when appropriate.

Add note that output in doc might not always match output if following along in tutorial (for illustrative purposes). That said, update output to better match actual output.

Ensure that :key-names do not wrap in tables.

Link to other docs when helpful.

Fix some typos.

Edits for clarity.

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@tengstrand, ready for review and feedback! As always, please read the commit comment carefully before reviewing.

[lread]

Ok @tengstrand, I merged in your changes and addressed all review feedback!