We have further cases where we have both a `foo.md` an `foo/`. This results
in `food.md` being hidden. Move `foo.md` to `foo/_index.md` so that all
content is accessible, working on the assumption that the contents of
`foo/` are sub pages.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>

 - Move reference_hardware.md to be index so that it's rendered.
 - Add extra reference to hardware on main page.
 - Update links.
 - Correct links to pictures.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>

Rewrite links to the test cases for their actual location and remove links
to the now unusable templates. This allows the wiki category and templating
pages, which no longer function as expected as it's no longer a wiki.

The test case documentation is out-of-date, but rewriting this is out of
scope. See T6736.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>

The release documentation currently live under `content/<version>/`, move
it into it's own section. This cleans up the content directory and may
enable us to do fancy things with Hugo templating further down the line.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>