ev-recent-view: Added bookshelf view for recent documents

* Files are added to the bookshelf only if they exists
* Save thumbnails and metadata
* Use gtk_recent_info_get_modified instead of
  gtk_recent_info_get_visited for ordering the recent items.
shell: Integrate recent view into the main window

* Allow switching between document and bookshelf
* It seems more natural as we 'toggle' between the bookshelf the
currently open document.
shell: Implement a different toolbar for bookshelf/recent view

Added a new EvMinimalToolbar which is displayed while in
bookshelf/recent view, instead of the full regular toolbar.
ev-window: Removed the recent menu list

Since we have EvRecentView now, there is no use of the menu of recent items.
Removing it.