added PublishWorkflowListener

see https://github.com/symfony-cmf/RoutingExtraBundle/pull/58

we can then remove the logic from the ``ContentController``:
https://github.com/symfony-cmf/ContentBundle/pull/22

i would suggest to not implement the ``PublishWorkflowInterface`` in the ``Route``, maybe not even in the ``StaticContent``/``Page`` classes anymore. that being said .. while i want to keep the dependencies of RoutingExtraBundle as small as possible, I have no concern over the CoreBundle dependency in ContentBundle and SimpleCmsBundle

/cc @elHornair @dbu