Documentation enhancements

Making metadata:
- more consistent
- more specific (fixed copy pasting)
- refine coverage

Insecure information cleanup

Removing no longer used files:
- mkdocs is gone
- the registry diagram is not used, and is a bit silly :)

Minor fixes

Fixing links

Recipes:
- harmonized code sections style to the rest of the docs
- harmonized recipe "style"
- listing new recipes

Enhance deploying

Signed-off-by: Olivier Gambier <olivier@docker.com>

docs/spec/api.md

@@ -1,8 +1,8 @@
 <!--[metadata]>
 +++
-title = "Docker Registry HTTP API V2"
-description = "This is a specification for the API."
-keywords = ["registry, service, driver, images, storage,  api"]
+title = "HTTP API V2"
+description = "Specification for the Registry API."
+keywords = ["registry, on-prem, images, tags, repository, distribution, api, advanced"]
 [menu.main]
 parent="smn_registry_ref"
 +++
@@ -21,7 +21,7 @@ of this API, known as _Docker Registry HTTP API V2_.
 While the V1 registry protocol is usable, there are several problems with the
 architecture that have led to this new version. The main driver of this
 specification these changes to the docker the image format, covered in
-docker/docker#8093. The new, self-contained image manifest simplifies image
+[docker/docker#8093](https://github.com/docker/docker/issues/8093). The new, self-contained image manifest simplifies image
 definition and improves security. This specification will build on that work,
 leveraging new properties of the manifest format to improve performance,
 reduce bandwidth usage and decrease the likelihood of backend corruption.