Support for unique indexes and multicolumn indexes

[vladiscripts]

Could you add the ability to read existing unique indexes and multicolumn indexes from the current database model? In order not to list them each time in insert (keys) and upsert (keys).

[pudo]

It'd be kind of cool to use a unique index for the upsert when it is available, would love to see a PR to do that. Essentially, I guess it would make the keys argument optional.