o.c.ui.menu.app: Explicitly add 'additions', 'group.editor' to Toolbar

.. because otherwise the tool bar gets messed up under E4. For E3, this
doesn't matter, but best keep the sources the same.
Merge pull request #454 from ControlSystemStudio/bug453

o.c.ui.menu.app: Explicitly add 'additions', 'group.editor' to Toolbar