* Update device plugin docs for Kubernetes 1.14
& related pages
This change is mainly about feature-state shortcodes & similar.
(if there's a way to get the short version string, eg "1.14" rather
than "v1.14", then that could go in place of the hard coded value
in this commit).
* Fix code block formatting
eg code blocks incorrectly marked as:
```shell
* Use glossary shortcodes where appropriate
* Hyperlink to Prometheus
* Tidy Markdown formatting
* Change example vendor domain name
Use a name inside ".example" to highlight that this is a DNS
domain name.
* Reword device plugins documentation
* Tweak headings for device plugins
* Add "what's next" to device plugins docs
* Tweak wording for device plugins docs
* Add KubeVirt device plugins
Tim Bannister
chenrui
Damini Satya