lib/application: improve URL building algo

When running on Unix and no hostname is specified, use `0.0.0.0`
as the hostname instead of `localhost`.

When running on Windows and the hostname is either not specified or
it is `0.0.0.0` or `::`, use `localhost` in the URL. The reason is
that Windows cannot open URLs using `0.0.0.0` as a hostname.
Merge pull request #659 from strongloop/fix/url-generated-on-windows

lib/application: improve URL building algo