Change to the new namespace

Cherry-picked from the old pull request. No Javadoc this time :)

This includes the needed changes to load on both a server and client, as well as play in singleplayer - I haven't tested it playing on multiplayer yet, but there's no reason it shouldn't. If you'd like, I can update my server (still in development) to mirror these changes and let you know if it works. It was only two changes IIRC, one for the proxy class location and one for the design handler to open the correct directory instead of one that no longer exists after the namespace change

Signed-off-by: Cruz Julian Bishop <cruz@techern.com>
What does this change do?