[O] Better inline image scrolling

[Brice Waegenire]

Scrolling of inline images in org-mode is cumbersome, especially when
you have several of it in sequence, on a small screen. For example
when you are in a buffer after a image, not visible at the moment, and
you scroll up with either the C-p or your mouse wheel, it get
displayed entirely instead of bit by bit, from it's bottom to it's
top.

Could it be possible to display images as several lines, instead of a
unique one, with insert-sliced-image
(http://www.gnu.org/software/emacs/manual/html_node/elisp/Showing-Images.html)
like emacs-ipython-notebook
(https://github.com/tkf/emacs-ipython-notebook) do when (setq
ein:slice-image t) is set?