Overwrites images of same name in dest

[FraidOfWater]

The program currently overwrites images with the same name. Regards "Move and moveall" from sortimages_multiview.py. Example: "test.png" in source and "test.png" in dest, the one in source will overwrite the one in dest, deleting it. Just a fair warning for any users.
We should check whether an image with that name already exists in destination before moving. We could do
temp = os.path.join(destpath, self.name.get()) if os.path.exists(temp): return ("")
before me move the picture to cancel the move.

[FraidOfWater]

Made a pull request to fix it.