FEATURE: Followup new Neos.Workspace.UI

[Sebobo]

Planned features for 9.0 or 9.x after initial merge of the new module:

• Force delete of workspaces with rebase of subs-workspaces and dropping unpublished changes
• Move and update user stories for module from package to wiki or some other good place
• Define change base workspace and document it (originally introduced via e0b8408)

Optionals

• reimplement rebase personal workspace and redirect to edit a change in the review mode