Add the release schedule (a bit late) and the release notes for v2019.2.

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>

The wiki markup made it so that fragment links needed to be named as per
the link name, thus enforcing the link test for such URLs started with a
hash. As we are not using a wiki anymore, this is not the case and we can
clean out the hashes to make the text more readable.

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

There are a number of badly formatted links that don't point correctly to
resources or point to resources that aren't available. Where possible
correct the links, if this is not possible remove or neuter the link to
preserve as much as possible.

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

A number of files in the `content/` directory are either unlinked (and
therefore hidden) or would have contained a message (generated by a wiki
template) stating they were obsolete and pointing to the updated location.

 - Move the unlinked documents into guidelines so that they are at least
   accessible via the automatic list, link if a quick location can be
   found.
 - Remove the obsolete pages and update the links to point to the correct
   location.

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

A number of documents used to be marked as work in progress on the wiki.
Move these to their own folder to make this distinction.

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

The 19.03 release was released under the new versioning convention as
`v2019dev0`, point to this release and remove hanging 19.03 release
schedule page.

Add 17.12.1 release to the list fo releases as it's not there.

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

During conversion, when we hit a dangling reference to a page that didn't
exist, a placeholder was added for that page to allow Hugo to generate the
site. We now want to remove these pages.

 - Test cases: Replaced with "obsolete test" page.
 - Old bug links: Converted to broken link.
 - Link to specs removed.
 - Links to yet-to-be-created release notes removed.

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

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>