Support Redirect Mode

Currently, MaxScale operates only as a proxy, which enables many advanced features, but comes with the drawback of requiring twice the network traffic, since everything must go client->maxscale->db and vice versa. It would be helpful in some use cases to have the clients get routed directly to the DB, such that they only hit the MaxScale server at connect time; the MaxScale server would instruct them to go directly to a particular DB server, based on rules set up in the configuration file, and from then on, for the life of that session, all communication is directly between the client and the DB, without MaxScale involved.