Merge branch 'hotfix/3.0.3'
Added the hotfix/3.0.4 branch
Added lazy template loading for newsletter mail templates
Handle `$_GET['auto_item']` when rebuilding URLs (also see e225fce79952faf9a09bb37e504941cea9b3aa00)
Merged the latest version 2.11 changes
Copy all content elements if pages are duplicated with childs (see #5241)
The table sorter did not work if jQuery and MooTools were active (see #5228)
Handle the case that `glob()` returns `false` (see #5226)
Added the missing `UserGroupModel` class (see #5218)
Show the "edit header" button even if it is disabled
Added the Lithuanian translation source files
Added the Bulgarian translation source files
Added the Croatian translation source files
Updated all language files
Prevent the auto_item feature from generating duplicate content (see #4012)
Merged the latest version 2.11 changes
Added support for more advanced media queries (see #5236)
Make the jQuery accordion behave like the MooTools version (see #5251)
Merge branch 'hotfix/3.0.4' into develop

Conflicts:
	system/config/constants.php
	system/docs/CHANGELOG.md
	system/modules/calendar/dca/tl_calendar.php
	system/modules/core/dca/tl_article.php
	system/modules/core/dca/tl_form.php
	system/modules/core/dca/tl_style_sheet.php
	system/modules/faq/dca/tl_faq_category.php
	system/modules/news/dca/tl_news_archive.php
	system/modules/newsletter/dca/tl_newsletter_channel.php
	system/modules/repository/themes/default/backend.css