The key-value store provides a simple persistence layer for the players.
This class provides the methods to set, get and unset key-value pairs. This is executed within the context of the currently logged in player.
Size: there are no limits to the number of stored key/values as long as the total size is less than 256kb.
Requests: Set/Get/Unset can be called unlimited amount of times but the execution may be throttled.