Extended translations system for arrays & extension

Extended the base Laravel translation system to
allow a locale to be based upon another.

Also adds functionality to take base & fallback locales into account when fetching
an array of translations.

Related to work done in #1159

resources/lang/de_informal/common.php

@@ -1,11 +1,9 @@
 <?php
-$de_formal = (include resource_path() . '/lang/de/' . basename(__FILE__));
 
-$de_informal = [
+// Extends 'de'
+return [
     /**
      * Email Content
      */
     'email_action_help' => 'Sollte es beim Anklicken der Schaltfläche ":action_text" Probleme geben, öffne die folgende URL in Deinem Browser:',
-];
-
-return array_replace($de_formal, $de_informal);
+];