Feature: Adding an empty GtkBox on the top of the image

This feature have the purpose to access graphically the functionalities of plugins added in eog. By default, the box is hidden to avoid a change in the behaviour of Eog and can be display via the show submenu. It will be possible to insert plugins inside the box with the method eog_window_get_boxtool and in the menu.

I'm working for Ordissimo who sold laptop with a derivative of debian on it to 100,000 seniors and we intend to add Eog as the official image viewer for his simplicity (see our our website for more information)