Block: Clean up internal constructor inconsistencies

I don't dare look how big this commit is or how many bugs it introduced...

src/pocketmine/block/Cobweb.php

@@ -29,20 +29,10 @@ use pocketmine\item\ItemFactory;
 
 class Cobweb extends Flowable{
 
-	protected $id = self::COBWEB;
-
-	public function __construct(){
-
-	}
-
 	public function hasEntityCollision() : bool{
 		return true;
 	}
 
-	public function getName() : string{
-		return "Cobweb";
-	}
-
 	public function getHardness() : float{
 		return 4;
 	}