[fixed] save selected / images

[micheus]

Yeah, it looks like all images are saved even if not used by the object's material.

But, it works that way since I knew Wings3D. Maybe it was decided to the user decide to remove the unwanted images in the new project. If it was removed and the user was intending to use it in the new file, then he would needed to add each image again (although, now a days we can select multiple images to import )

I'm not sure we can consider that a bug.