PUBDEV-4729-sw22-release (#1474)
PUBDEV-4729-sw22-release (#1474)

* PUBDEV-4729-sw22-release

- Added links for the Sparkling Water 2.2 release, including links to
github repos and scaladocs.
Driveby fix: Added a link to XGBoost documentation under supervised
algorithms.
Tested site in three browsers.

* Updating SW links

Updated Sparkling Water scala doc links to the latest release. Also
changed md links to rst files.

michalkurka/h2o-3,spennihana/h2o-3,mathemage/h2o-3,h2oai/h2o-3,h2oai/h2o-dev,h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-3,mathemage/h2o-3,mathemage/h2o-3,h2oai/h2o-dev,michalkurka/h2o-3,h2oai/h2o-dev,michalkurka/h2o-3,h2oai/h2o-dev,h2oai/h2o-dev,mathemage/h2o-3,spennihana/h2o-3,spennihana/h2o-3,h2oai/h2o-3,spennihana/h2o-3,spennihana/h2o-3,michalkurka/h2o-3,spennihana/h2o-3,h2oai/h2o-dev,michalkurka/h2o-3,h2oai/h2o-3,mathemage/h2o-3,michalkurka/h2o-3,spennihana/h2o-3,mathemage/h2o-3,h2oai/h2o-3,h2oai/h2o-3,michalkurka/h2o-3,mathemage/h2o-3,h2oai/h2o-dev