Change Log:
-Added a permission to allow players to specify the amount of xp they drop
-The default value for this permission is op only
-If a player has this permission, they can use /dropxp <number of levels>
-Doesn't change anything if "requireThickPotion" is true
-Added info to XP Potions that shows how many levels its worth (starting from level 0)
-Changed the appearance of thick potions when they are created in a brewing stand, but only if requireThickPotion is set to true
-Slightly changed the color of XP potions
-Removed the minimum 1 level requirement to drop xp, dropping xp now stores all xp