Allow writing of uuid to image w/o making a copy of the original

By default, writing uuid to the image metadata creates a copy of the original file with _original appended. This is the default behaviour of Exiftool, which is used internally to write Exif metadata.

Exiftool allows writing Exif metadata directly to the original without creating a copy using the option -overwrite_original. I would propose to allow this also in MariQT by passing a parameter overwrite_original=False to mariqt.image.writeUUIDtoPhoto

From https://exiftool.org/forum/index.php?topic=5514.0:

The option to do this is -overwrite_original There will be no speed increase, but the _original files will not be created. You can use the -delete_original option to clean up any "_original" files you may have already generated. Read the application documentation for more details about these options.