Move #isNpc method to PlayerUtils

- After dropping our hook to CombatTagPlus it is not relevant for it to be in PluginHooksService anymore

src/main/java/fr/xephi/authme/util/PlayerUtils.java

@@ -39,4 +39,15 @@ public final class PlayerUtils {
     public static String getPlayerIp(Player p) {
         return p.getAddress().getAddress().getHostAddress();
     }
+
+    /**
+     * Returns if the player is an NPC or not.
+     *
+     * @param player The player to check
+     *
+     * @return True if the player is an NPC, false otherwise
+     */
+    public static boolean isNpc(Player player) {
+       return player.hasMetadata("NPC");
+    }
 }