Reading for content; editing for consistency.

ref:
https://github.com/civicrm/civicrm-dev-docs/pull/217#issuecomment-314945998

ref:
https://github.com/civicrm/civicrm-dev-docs/pull/217#discussion_r127111272

This was in the general "buildkit" page, and I think it fits better in
the specific "civibuild" page.

This is a direct copy-paste from one section of the guide to another,
without any edits. When someone is installing buildkit, these steps are
easy to miss if they're located in the civibuild file.

We don't really need the two bulleted lists:
 * In context, the previous section should give hints about what this means.
 * If the context isn't clear enough, then the links provide more concrete description.

1.  The title for section `civicrm.settings.php; settings.php;
wp-config.php` is very long. Split the section -- a longer one
which discusses `civicrm.settings.php` in more depth, and a shorter
which discusses similar files briefly.

2.  Add a section for `civibuild.conf`.

This way MkDocs will be able to report errors for broken links

Done with:

perl -0777 -i -pe \
's@(?<!!)\[([^\]]*)\]\((?!https?://)(?!mailto:)(/(?:(?:(?:/(?![\)#]))|[^/)#])(?!.md))+)/?(#[^)]*)?\)@[$1]($2.md$3)@gm' \
`find . -name '*.md'`

Migrated from the following two sources

https://github.com/civicrm/civicrm-buildkit/blob/d20229ac9f63aaf183687157a5e655c953b81f5e/doc/daily-coding.md#housekeeping
https://civicrm.stackexchange.com/questions/17717/how-do-i-upgrade-civicrm-on-a-local-site-that-i-installed-with-buildkit-civibuil/17721#17721

Not adding internal redirects because these pages are so new.