pushmanager link-generation is not proxy-aware

[hashbrowncipher]

pushmanager has the capability to generate links to itself, but it uses the server and port it has bound to in order to generate those links. When pushmanager is run behind a proxy, the port it binds to and the port that users use to access it (i.e. the port the proxy binds to), are not the same.

When I've dealt with this issue in other proxied webapps, I have added configuration knobs that allow me to inform the app "bind to this host and port, but generate links for this host and port". Typically I would then set the webapp to bind to "127.0.0.1:" when run in production.