Fixed an issue where FlagGUI throws a NPE when the owner is offline.
Additions
Added a system that will allow you to set an expiration time to a claim. When you set this expiration time, when a player has been offline for longer than his claim's expiration time, his claim will be deleted to save resources and memory.
Added the /claim admin deletionQueue that will open a list of the claims that will expire in the next 30 minutes...