1) Update doc links according to OpenStack document migration
2) Use https instead of http for docs links
Change-Id: I04591d5c4a7cdb3395d4c90237df39a1eb281580
* 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: I5c741481d9520222fd26464aeace7c388e63c214