Updated front page for docs site (master) (#2627)
Updated front page for docs site (master) (#2627)

- Updated links for Enterprise Steam and Steam downloads
- Added AutoML to list of algos
- Added RStudio cheat sheet
michalkurka/h2o-3,h2oai/h2o-3,michalkurka/h2o-3,h2oai/h2o-dev,michalkurka/h2o-3,h2oai/h2o-3,h2oai/h2o-3,michalkurka/h2o-3,h2oai/h2o-3,h2oai/h2o-dev,h2oai/h2o-dev,h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-dev,h2oai/h2o-dev,michalkurka/h2o-3,michalkurka/h2o-3,michalkurka/h2o-3,h2oai/h2o-dev,h2oai/h2o-dev