Backport last fixes before releasing 3.4.0

Last fixes before releasing 3.4.0 (Öffentlichkeitsgesetz) Release:

- https://github.com/4teamwork/opengever.core/pull/503
- https://github.com/4teamwork/opengever.core/pull/504
- https://github.com/4teamwork/opengever.core/pull/505