Shared PortBindingInfo abstraction for all servers.

Includes `scheme`, `host`, and `port`, and produces a `url` so that could be opened in a web browser.

Also updates the browser code since we can do that now, and adds a build intsruction for Java 1.6.
 
I think it would be confusing to have `jetty.PortBinding` and `netty.PortBinding` extend from `util.PortBinding` so I decide to have this be about the "info". And for the deprecated servers, it really is just info and not a real binding.