bookshelf: Added bookshelf view for recent documents

Files are added to the bookshelf only if they exists
bookshelf: 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: Rename class from EvBookshelf to EvRecentView

EvRecentView sounds more appropriate based on feedback with
KaL.
ev-recent-view: Make variables and arguments meaningful

* Use 'model' instead of 'list_store'
* Use 'ev_recent_view' instead of 'self'
* Use 'EvRecentView *' in the parameter instead of the generic
  gpointer user_data for callbacks.
* Make the code conform Evince convention to name objects
* Rename tree_path to make its purpose clearer
* Use 'pressed_item_tree_path' instead of 'button_press_item_tree_path'
  to make clear the intention of use.
* Use 'result' instead of 'res'
* Remove unnecesary use of label and string functions.  Based on
  feedback from https://bugzilla.gnome.org/show_bug.cgi?id=633501
ev-recent-view: Use signal handler_id instead of disconnect_by_func
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.