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/validation.php

@@ -1,8 +1,6 @@
 <?php
-$de_formal = (include resource_path() . '/lang/de/' . basename(__FILE__));
 
-$de_informal = [
-
-];
-
-return array_replace($de_formal, $de_informal);
+// Extends 'de'
+return [
+    //
+];