Replacing old inventory protecting with safe packet modifications using ProtocolLib.

Instead of clearing the inventory of players and storing it's contents in a file, we now prevent
the server from sending the inventory packet if the player is not logged in. The player will
see a empty inventory, but has still his items stored on the server. Therefore we don't
need to modify the player's inventory and we won't make any inventory corrupted.

Fixes Xephi/AuthMeReloaded#203,
Fixes Xephi/AuthMeReloaded#193,
Fixes Xephi/AuthMeReloaded#191,
Fixes Xephi/AuthMeReloaded#148

Remove dead code + Fix empty inventory on the unregister command

Fix NPE if ProtocolLib isn't enabled or installed

src/main/java/fr/xephi/authme/commands/UnregisterCommand.java

@@ -18,7 +18,6 @@ import org.bukkit.command.Command;
 import org.bukkit.command.CommandExecutor;
 import org.bukkit.command.CommandSender;
 import org.bukkit.entity.Player;
-import org.bukkit.inventory.ItemStack;
 import org.bukkit.potion.PotionEffect;
 import org.bukkit.potion.PotionEffectType;
 import org.bukkit.scheduler.BukkitScheduler;
@@ -34,7 +33,7 @@ public class UnregisterCommand implements CommandExecutor {
 
     public UnregisterCommand(AuthMe plugin) {
         this.plugin = plugin;
-        this.playerCache = new JsonCache(plugin);
+        this.playerCache = new JsonCache();
     }
 
     @Override
@@ -79,8 +78,7 @@ public class UnregisterCommand implements CommandExecutor {
                                     player.teleport(tpEvent.getTo());
                                 }
                             }
-                            player.getInventory().setContents(new ItemStack[36]);
-                            player.getInventory().setArmorContents(new ItemStack[4]);
+                            
                             player.saveData();
                             PlayerCache.getInstance().removePlayer(player.getName().toLowerCase());
                             if (!Settings.getRegisteredGroup.isEmpty())