Secured the handling of InventoryClickEvent for panels (#761)

* Fix Challenges GUI issue 132

Fixed BentoBoxWorld/Challenges#132
This issue happens because AnvilGUIClick event was processed after BentoBox registers new Panel. 
I add extra check in InventoryClickEvent that not only checks if user has opened panel, but also compares if event and panel has the same inventory, before processing it as BentoBox Panel.

* Removed the unneeded PlayerKickEvent

src/main/java/world/bentobox/bentobox/listeners/PanelListenerManager.java

@@ -12,6 +12,7 @@
 import org.bukkit.event.inventory.InventoryClickEvent;
 import org.bukkit.event.inventory.InventoryCloseEvent;
 import org.bukkit.event.inventory.InventoryType.SlotType;
+import org.bukkit.event.player.PlayerKickEvent;
 import org.bukkit.event.player.PlayerQuitEvent;
 import org.bukkit.event.server.PluginDisableEvent;
 import org.bukkit.inventory.InventoryView;
@@ -31,7 +32,8 @@ public void onInventoryClick(InventoryClickEvent event) {
         InventoryView view = event.getView();
 
         // Open the inventory panel that this player has open (they can only ever have one)
-        if (openPanels.containsKey(user.getUniqueId())) {
+        if (openPanels.containsKey(user.getUniqueId()) &&
+            openPanels.get(user.getUniqueId()).getInventory().equals(event.getClickedInventory())) {
             // Cancel the event. If they don't want it to be cancelled then the click handler(s) should
             // uncancel it. If gui was from our environment, then cancel event anyway.
             event.setCancelled(true);