allow database as optional connection parameter
allow database as optional connection parameter

ajcrowe/go-mssqldb,NicheInc/go-mssqldb,denisenkom/go-mssqldb,bhcleek/go-mssqldb,justinyaoqi/go-mssqldb,ArtemTeleshev/go-mssqldb,courtf/go-mssqldb,gaspardle/go-mssqldb,XTXMarkets/go-mssqldb,colonyamerican/go-mssqldb,sndnvaps/go-mssqldb