Reload support

I wrote this back in 2011 and never submitted a pull request... better late than never!

This changeset adds the ability to reload the server configuration without restarting it. As a supported feature of minecraft server and craftbukkit, this would be an ideal feature to implement.

The original work has been modified to make use of the new screen interface functions, and so should be up to date with the style of the rest of submitted code.