Separate use-item action from PlayerInteractEvent

This solves the age-old issue of PlayerInteractEvent firing twice when a player clicks a block with an item in the hand.

API changes:
- Removed PlayerInteractEvent constants LEFT_CLICK_AIR, RIGHT_CLICK_AIR and PHYSICAL.
- PlayerInteractEvent no longer fires when the player right-clicks the air.
- Added new event PlayerItemUseEvent.

src/pocketmine/event/player/PlayerItemUseEvent.php

@@ -0,0 +1,69 @@
+<?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\event\player;
+
+use pocketmine\event\Cancellable;
+use pocketmine\item\Item;
+use pocketmine\math\Vector3;
+use pocketmine\Player;
+
+/**
+ * Called when a player uses its held item, for example when throwing a projectile.
+ */
+class PlayerItemUseEvent extends PlayerEvent implements Cancellable{
+
+	/** @var Item */
+	private $item;
+	/** @var Vector3 */
+	private $directionVector;
+
+	/**
+	 * @param Player  $player
+	 * @param Item    $item
+	 * @param Vector3 $directionVector
+	 */
+	public function __construct(Player $player, Item $item, Vector3 $directionVector){
+		$this->player = $player;
+		$this->item = $item;
+		$this->directionVector = $directionVector;
+	}
+
+	/**
+	 * Returns the item used.
+	 *
+	 * @return Item
+	 */
+	public function getItem() : Item{
+		return $this->item;
+	}
+
+	/**
+	 * Returns the direction the player is aiming when activating this item. Used for projectile direction.
+	 *
+	 * @return Vector3
+	 */
+	public function getDirectionVector() : Vector3{
+		return $this->directionVector;
+	}
+}