provide information about our `:engines` through our main MetabaseSettings which simplifies some things and removes the need for a /api/database/form_input endpoint.

use the GA code that is injected into the app dynamically and instrument our setup steps so we know if people fail on install.

update setup help link to go directly to the docs for the current version, not just the latest docs in general.

new setup process working end-to-end in React now.  still more to do, but all the pieces are in place now.