Implement the /world warp command
Support highlighting in success messages
Support removing worlds
Implement a Settings class, living alongside Configuration

Whereas Configuration is not mutable from within Mineground, the
Settings class will be mutable for features.
Load and save the default world to a setting.
Implement /world {classic, creative, survival}.

These will be the setters for the player-accessible /classic, /creative
and /survival commands.