Revert back to separated floor/wall sign

the conditionally useless properties are problematic.

src/block/WallSign.php

@@ -0,0 +1,61 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+*/
+
+declare(strict_types=1);
+
+namespace pocketmine\block;
+
+use pocketmine\block\utils\BlockDataSerializer;
+use pocketmine\block\utils\HorizontalFacingTrait;
+use pocketmine\item\Item;
+use pocketmine\math\Axis;
+use pocketmine\math\Facing;
+use pocketmine\math\Vector3;
+use pocketmine\player\Player;
+use pocketmine\world\BlockTransaction;
+
+final class WallSign extends BaseSign{
+	use HorizontalFacingTrait;
+
+	protected function writeStateToMeta() : int{
+		return BlockDataSerializer::writeHorizontalFacing($this->facing);
+	}
+
+	public function readStateFromData(int $id, int $stateMeta) : void{
+		$this->facing = BlockDataSerializer::readHorizontalFacing($stateMeta);
+	}
+
+	public function getStateBitmask() : int{
+		return 0b111;
+	}
+
+	protected function getSupportingFace() : int{
+		return Facing::opposite($this->facing);
+	}
+
+	public function place(BlockTransaction $tx, Item $item, Block $blockReplace, Block $blockClicked, int $face, Vector3 $clickVector, ?Player $player = null) : bool{
+		if(Facing::axis($face) === Axis::Y){
+			return false;
+		}
+		$this->facing = $face;
+		return parent::place($tx, $item, $blockReplace, $blockClicked, $face, $clickVector, $player);
+	}
+}