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.
PotionEffects do not get splashing effects, it's the ItemStack that defines whether the potion splashes or not.