Consumables refactor (#1796)

* Removed broken EntityEatEvents - these don't fit the pattern since they only apply to Human entities anyway. PlayerItemConsumeEvent and PlayerInteractEvent can be used for cancellation purposes, and plugins can do custom stuff without mess.

* Restrict item consuming to Living entities only

* Added FoodSource->requiresHunger()

* Only items implementing the Consumable interface can now be consumed.

* The effects from consuming items are now generic-ized by way of the Living->consume() function. This is overridden in Human to allow applying food and hunger.

* Fixed the hardcoded mess for buckets

src/pocketmine/item/Item.php

@@ -621,32 +621,6 @@ class Item implements ItemIds, \JsonSerializable{
 		return $this->block !== null and $this->block->canBePlaced();
 	}
 
-	/**
-	 * Returns whether an entity can eat or drink this item.
-	 * @return bool
-	 */
-	public function canBeConsumed() : bool{
-		return false;
-	}
-
-	/**
-	 * Returns whether this item can be consumed by the supplied Entity.
-	 * @param Entity $entity
-	 *
-	 * @return bool
-	 */
-	public function canBeConsumedBy(Entity $entity) : bool{
-		return $this->canBeConsumed();
-	}
-
-	/**
-	 * Called when the item is consumed by an Entity.
-	 * @param Entity $entity
-	 */
-	public function onConsume(Entity $entity){
-
-	}
-
 	/**
 	 * Returns the block corresponding to this Item.
 	 * @return Block