WorldBorder and Potions

Added new method to set the startingDiameter, endDiameter and the time it will take [void setDiameter(double startDiameter, double endDiameter, long time);]
Added Splash potion option.
Changed Radius to Diameter.
Changed get/setBlockBuffer to get/setBuffer and changed the return and parameter to double as it is not measured in whole blocks.
Splash is defined in PotionEffect (class ws field private boolean e;), and yes it is also defined in the item but you only have to add 1 to the damage value. It will also be easier for the Potion builder to take if it is splashable so it can build the item without having to then add yet another useless line in the API.