multiview: image node now has a list of available views + code cleanup +
set prints in openexr to be under a exr_printf function

Also we now store the name and name_internal (for ui) in the renderpass
I needed that for the Image Node, but I will also need it for the
UV/Image editor.

Image Node still needs to know how to use the views, but that's next.

bug: somehow I need to re-load the image to have the ui re-generated :/
not sure why