Feature/merge 3 0 develop (#298)

* merging 3.0 into develop

* N°5102 - Allow to send emails (eg. notifications) using GSuite SMTP and OAuth
* migration to iTop 3.1

Co-authored-by: Eric Espie <eric.espie@combodo.com>

dictionaries/ui/layouts/page-content/pl.dictionary.itop.page-content.php

@@ -0,0 +1,8 @@
+<?php
+/**
+ * @copyright   Copyright (C) 2010-2021 Combodo SARL
+ * @license     http://opensource.org/licenses/AGPL-3.0
+ */
+Dict::Add('PL PL', 'Polish', 'Polski', [
+	'UIBlock:Error:CannotGetBlocks' => 'Could not retrieve blocks from content area "%1$s" as it does seem to exists for page content "%2$s"~~',
+]);