Gatekeeper

Breaking: the server and the client must both be on 1.1. A 1.0 client is turned away with a message naming the version to install.

• Paper servers are now supported by a companion plugin. This same client mod authenticates against either platform.
• The handshake moved from plugin messaging channels to vanilla cookies (protocol version 2). The client no longer announces a channel on every server it joins, so servers that do not use Gatekeeper are told nothing about it.
• Fixed: a player who authenticated but dropped before reaching the world could block admin approval for their account until the server restarted.