Versioning-Compare mode: quick restore button is missing

Currently there is no "quick restore" button in compare mode in order to be able to rapidly restore the current version being loaded on the page.

I think that an additional toolbar which would be only loaded in compare mode and which would list the date and version number of the current page being displayed combined with quick restore button would be quite interesting to add.

We could optionnaly combine such a new toolbar with the side-by-side views and options (if they are displayed not really side by side but as two "tabs") in such a toolbar.

Such a toolbar would only appear in compare mode (which I think is possible if I remember correctly the spec of Khaeld regarding the toolbars)