Clean up hierarchy of rails

detector rail has fundamentally different functionality than activator and powered rails, so it's misleading to present the same APIs for both.
detector rail's 'powered' state is better referred to as 'activated', since it means the detector rail is actually _producing_ power, and not _receiving_ power.

src/block/PoweredRail.php

@@ -23,5 +23,8 @@ declare(strict_types=1);
 
 namespace pocketmine\block;
 
-class PoweredRail extends RedstoneRail{
+use pocketmine\block\utils\RailPoweredByRedstoneTrait;
+
+class PoweredRail extends BaseRail{
+	use RailPoweredByRedstoneTrait;
 }