As with the backend form, a user might like to change the name of an
instance. The new form and its actions are also adjusted to suit the new form interface.
refs #5525
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
Johannes Meyer
Eric Lippmann
Matthias Jentsch
Jannis Moßhammer