Feature: Add option to only list available servers

It would be great if instead of listing all the unavailable servers in the server list, there should be a setting to hide non available servers. I can imagine why this is not done by default, it's great to show off all the possible locations, but it would be much more intuitive to allow users to hide these, at least in an opt-in basis. This is not only applicable for the Android client, but all clients.