Add server-side management commands

[IotaBread]

Enigma currently doesn't have any way to manage a server, dedicated or integrated, through any kind of UI. Things like saving, reloading or dropping mappings are impossible to do in a dedicated server, and probably don't work as they should for integrated ones. User management is also something both server implementations lack.

A command system, similar to Minecraft's but way simpler, would be a good fit for these tasks. A remote "console" protocol could be developed to manage dedicated servers, while integrated ones could be managed directly from the enigma swing UI.