Surface index info for relation databases

[peterthesling]

For postgres, mysql, and other relational DBs, we’re not surfacing or scraping index information in any way, which could be useful for those on these sorts of DBs to see. Robert found a nice stack question (https://stackoverflow.com/questions/2204058/list-columns-with-indexes-in-postgresql) that gives rough queries on how to do this in postgres. It seems that the markdown rendering part probably needs to be refactored first.

[peterthesling]

I'll start working on this in the next days.