force a identifier::Schema to be constructed with a identifier::Catalog. This is close to the final 'big' part for CATALOG support. We also have to modify all around the server that creates identifier::Schema so it does so properly. Since a single Session cannot span schemas, we get off a wee bit easy :) The big limitation in this patch is that INFORMATION_SCHEMA and DATA_DICTIONARY only appear in the LOCAL catalog (and this really needs to be fixed before CATALOGs other than LOCAL are supported).