[paulbalandan]

Description
Applies the user guide sweep to the pages and lines that exist only on 4.8, so the develop sweep merges into 4.8 without conflicts.

• Fixes grammar, awkward wording and heading underline lengths in the new pages and added lines.
• Uses US spelling (colour, behaviour, honour) to match the rest of the guide.
• Wraps unmarked code in double backticks and unmarked paths in double asterisks.
• Wraps prose at 120 characters, and joins wrapped entries in changelogs/v4.8.0.rst into one-liners.

make html has 0 warnings, the rendered pages have the same text apart from the spelling changes, and the docs-update converter passes on all pages.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value (without duplication)
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide