Prepare the incoming documentation refactoring, ensuring the files used by a doc page
are correcly moved together with the page, avoiding broken links during the reorganisation.
Partial backport of f7bedfce2e
to ease forward-ports
- Removed the numbering from headings because it was either inconsistent, breaking the implicit hyperlink target or useless.
- Fixed incorrect heading formattings.
- Replaced hand-written flows by the :menuselection: directive
