Added Block->getDropsForCompatibleTool(), removed lots of boilerplate code from subclasses

The function name is a little long-winded, but that can always be refactored later if needed. This provides a way for blocks requiring specific tools to override drops with non-standard stuff without needing to worry about what tool type was used.

It's also possible that passing the Item used here is actually entirely redundant, but again that can be fixed later.

src/pocketmine/block/Block.php

@@ -434,14 +434,25 @@ class Block extends Position implements BlockIds, Metadatable{
 	 */
 	public function getDrops(Item $item) : array{
 		if($this->isCompatibleWithTool($item)){
-			return [
-				ItemFactory::get($this->getItemId(), $this->getVariant(), 1)
-			];
+			return $this->getDropsForCompatibleTool($item);
 		}
 
 		return [];
 	}
 
+	/**
+	 * Returns an array of Items to be dropped when the block is broken using the correct tool type.
+	 *
+	 * @param Item $item
+	 *
+	 * @return Item[]
+	 */
+	public function getDropsForCompatibleTool(Item $item) : array{
+		return [
+			ItemFactory::get($this->getItemId(), $this->getVariant(), 1)
+		];
+	}
+
 	/**
 	 * Returns the item that players will equip when middle-clicking on this block.
 	 * @return Item