Would be possible to accept the URI as a valid connection string?

postgresql://[user[:password]@][netloc][:port][,...][/dbname][?param1=value1&...]

This is how Heroku provides access to its databases, and due the fact the values can (will?) change without announcement, it becomes quite cumbersome to manage it to the current "key value" format.

If you guys think it's a good idea, I would be happy to submit a PR to enhance the NpgsqlConnectionStringBuilder class.

Thanks!