adding TLS mutual authentication to vertica-sql-go

[ehrt74]

Hello! I'd like to add tls to vertica-sql-go. Probably best to implement it like in the mysql-library (see RegisterTLSConfig here: https://github.com/go-sql-driver/mysql/blob/3b935426341bc5d229eafd936e4f4240da027ccd/utils.go)

[vodrazka]

oh yes! +1

[ldrozdowski]

+1