Option to require admin approval for new edits

[Nutomic]

There should be an option that new article edits need to be approved by an admin before being merged and published. This way admins can check for spam or troll edits and effectively eliminate this problem. It requires a queue of pending edits and a way for admins to view, approve and deny them. Editors should be notified about the result.

The approval option could be available per article, or per instance (then applying to all local articles), or both.