Implement publishing workflow for published pages#5

Currently, a publishing workflow only works for unpublished pages, not for published ones.

What’s included in a publishing workflow?

• Revisions, to roll back if an editor f’ed up.
• Publishing state, update content without updating published document.
• Permissions, only certain users can publish other can only contribute.

Maybe it’s good to clarify the idea, or maybe it’s me not understanding the general idea of a publishing workflow.