SPIGOT-840, SPIGOT-2522: [Draft] Add EntityPotionEffectChangeEvent

Discussion ongoing in PR #449

By: kaenganxt <kaenganxt@mc-anura.de>

paper-server/nms-patches/EntityZombieHusk.patch

@@ -0,0 +1,11 @@
+--- a/net/minecraft/server/EntityZombieHusk.java
++++ b/net/minecraft/server/EntityZombieHusk.java
+@@ -43,7 +43,7 @@
+         if (flag && this.getItemInMainHand().isEmpty() && entity instanceof EntityLiving) {
+             float f = this.world.getDamageScaler(new BlockPosition(this)).b();
+ 
+-            ((EntityLiving) entity).addEffect(new MobEffect(MobEffects.HUNGER, 140 * (int) f));
++            ((EntityLiving) entity).addEffect(new MobEffect(MobEffects.HUNGER, 140 * (int) f), org.bukkit.event.entity.EntityPotionEffectEvent.Cause.ATTACK); // CraftBukkit
+         }
+ 
+         return flag;