* Update CHANGELOG with release notes URL.
* Update README with new release number & name.
* Update metadata.json with new tag & dependencies.
* Add release note prelude for Mitaka.
* Update Reno release note to drop prelude.
* Improve release note landing page.
Change-Id: I55cb70b74940eeed95e911b4df24f8320f57fe6d
Emilien Macchi