1.5.7-SNAPSHOT

Fixed a bug where a newly created world throws an exception when adding a player to the whitelist (#33)
Achievements can now be deactivated (#32)
Messages are still displayed, however, these can be deactivated via the gamerule
It is now possible to set the gamerule for each world via MultiWorld.
The TabCompletion of /mw gamerule shows the current value for a gamerule with a number as value