Images are not overriden on re-export

Hello,

When exporting a scene with images everything is fine, but when i export again the same scene over the previous .dae file it does not overrides the images. Instead the old images are kept. This behavior looks strange. It would be better if the new images are saved over the old ones.

If the cause of the current implementation is security reasons (to do not "accidentally" override some other important files) it is possible to rename the textures folder from `images` to `{DAE filename}_images` or something similar.

Start by tracing the scene re-export path that writes the .dae file and its `images` texture folder. Reproduce exporting the same scene twice over one .dae file, then identify why existing images are retained. Done means the second export saves the new images while preserving the intended safety behavior around existing files.

Written by the indexing model from the issue text.