TYPO3 Core

Currently there's no nice way to show notices, information, success, warning, or error messages to the user.

In the ruby on rails world they have a thing they call flash messages. Introducing these to the TYPO3 backend also gives us a nice way to show mentioned messages.

The icons need to be placed in typo3/gfx/

Usage example (backend module context):

$flashMessage = t3lib_div::makeInstance(
    't3lib_FlashMessage',
    $message, $title, $severity
);
$this->doc->pushFlashMessage($flashMessage);

(issue imported from #M11684)