Add support for Italian and update language files.

resources/lang/it_IT/auth.php

@@ -0,0 +1,37 @@
+<?php
+declare(strict_types=1);
+/**
+ * auth.php
+ * Copyright (c) 2017 thegrumpydictator@gmail.com
+ *
+ * This file is part of Firefly III.
+ *
+ * Firefly III is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Firefly III is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Firefly III. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+return [
+    /*
+    |--------------------------------------------------------------------------
+    | Authentication Language Lines
+    |--------------------------------------------------------------------------
+    |
+    | The following language lines are used during authentication for various
+    | messages that we need to display to the user. You are free to modify
+    | these language lines according to your application's requirements.
+    |
+    */
+
+    'failed'   => 'Queste credenziali non corrispondono ai nostri record.',
+    'throttle' => 'Troppi tentativi di accesso. Per favore riprova tra :seconds secondi.',
+];