Store messages in the current user session to be able to fetch messages from
other controllers, so that the use can be redirected back to the index, instead
of staying in the original action
refs #5100
Authentication/Session.php and its Subclasses do not have a open/closed -state
anymore. Read will refresh the session, write will always write the changes,
and opening/closing will be handled internally.
refs #5101
As we decided to remove Zend_Session due to locking issues,
we have to implement our session handling here. This is
the basic, untested code which will be tested in the next step
refs #4265
