The daemon / dockerd reference, docker engine plugin documentation,
and the Docker Engine feature deprecation documentation was imported
into the Moby repository in [moby@b9ce036].
Remove the files from this repository, and replace them with (temporary)
stubs pointing to their new location.
[moby@b9ce036]: https://github.com/moby/moby/commit/b9ce036ac8bfd28855d8aabc53fa451ce2339e1b
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
