Fix individual images saving having color management applied to one views (caminandes bug)

(and some code shuffling around)

Note: the only part of save_image_doit that is not fully ok is when the
user save a stereo encoded format (e.g., Anaglyph) and has the 'save as
copy' option unchecked. Personally I think we shouldn't support this
combination (user looses data this way), or we should re-load the image
(which is not nice if the format is lossly like jpeg).
tasdfsdfas