Adds proper checking and odd case catching before teleporting players through artificial end portals

Adds a proper permission check to make sure players are allowed to teleport through the artificial portal
Adds a teleportation back to the entrance as the teleportation event cannot be properly cancelled
Adds a proper class for storing info about the teleportation

src/main/java/net/knarcraft/stargate/container/FromTheEndTeleportation.java

@@ -0,0 +1,43 @@
+package net.knarcraft.stargate.container;
+
+import net.knarcraft.stargate.portal.Portal;
+import org.bukkit.entity.Player;
+
+/**
+ * This class represents a player teleporting from the end to the over-world using an artificial end portal
+ */
+public class FromTheEndTeleportation {
+
+    private final Player teleportingPlayer;
+    private final Portal exitPortal;
+
+    /**
+     * Instantiates a new teleportation from the end
+     *
+     * @param teleportingPlayer <p>The teleporting player</p>
+     * @param exitPortal        <p>The portal to exit from</p>
+     */
+    public FromTheEndTeleportation(Player teleportingPlayer, Portal exitPortal) {
+        this.teleportingPlayer = teleportingPlayer;
+        this.exitPortal = exitPortal;
+    }
+
+    /**
+     * Gets the teleporting player
+     *
+     * @return <p>The teleporting player</p>
+     */
+    public Player getPlayer() {
+        return this.teleportingPlayer;
+    }
+
+    /**
+     * Gets the portal to exit from
+     *
+     * @return <p>The portal to exit from</p>
+     */
+    public Portal getExit() {
+        return this.exitPortal;
+    }
+
+}