Incorporating flash messages. Not exactly sure I should expect any there, but if so, I want to see them.
(cherry picked from commit a009c9c)
Instead of requiring the menu items to specify their access requirements explicitly, reworked the filter mechanism to hook into Symfony's native firewall mechanism. The changes also lead to different behaviour for menu entries that do not have associated link targets, those only get rendered if they have children which *do* have a link *and* can be accessed by the user. Among other things, this means that menu structures containing no link target will never pass the filter.
(cherry picked from commit 69f07eb)