Feature: #63453 - Template support for FlashMessagesViewHelper

Description

Template support for FlashMessagesViewHelper has been added. This allows to define a custom rendering for flash messages.

The new attribute as for the FlashMessagesViewHelper allows to specify a variable name, which can be used within the view helper's child elements to access the flash messages.

Example usage:

<f:flashMessages as="flashMessages">
	<ul class="myFlashMessages">
		<f:for each="{flashMessages}" as="flashMessage">
			<li class="alert {flashMessage.class}">
				<h4>{flashMessage.title}</h4>
				<span class="fancy-icon">{flashMessage.message}</span>
			</li>
		</f:for>
	</ul>
</f:flashMessages>