Update studio landing page and add all-new install flow docs.

bug: 27850063 (update system reqs for 2.0)
bug: 27725026 (update download page for 2.0)
bug: 23908299 (clean up download and get started)

depends on CL: Ibc4ddb4a6130ab8bd8d6044472022465829f2000

Change-Id: Id56ddec26e5701f69cd3e3ce7dc64cd28e98c8f3