Minor cleanup
ItemStack.compareItem now compares material types first
Created WorldGroup and WorldGroupManager classes
implemented the WorldGroupSettings configuration handler
Added method getWorldGroupManager to plugin.

Also removed references to AuctionQueue, since that will
be handled by the WorldGroupManager
Added relevant options to configuration. (WorldGroups disabled by default)
Implemented some methods related to world groups
Began integration of auction queues with world groups
Adapted AuctionCancel to use world groups.

Also added an appropriate message when attempting to cancel
an auction from the console.
Added a generic message for commands unavailable to console.
Implemented GroupCache to track which worlds a player is in after logout.
Adapted methods to work with the new world groups.
No need to implement ConfigurationHandler here
Began implementing channel system