Make driver/db-start-of-week be per-DB

[sbelak]

Currently we assume all the DBs using the same driver have the same start of week, which for very international organizations (or ones with a lot of legacy) might not be true.

[kaklakariada]

Please consider implementing this. Currently the API does not allow drivers to read the current setting for the start of the week from the database, see sources at https://github.com/metabase/metabase/blob/master/src/metabase/driver.clj#L741

A user of our Exasol driver got wrong results because of this, see exasol/metabase-driver#59.