[formatsort] Remove misuse of 'preference'

'preference' is to be used only when the format is better that ALL qualities of a lower preference irrespective of ANY sorting order the user requests. See deezer.py for correct use of this

In the older sorting method, `preference`, `quality` and `language_preference` were functionally almost equivalent. So these disparities doesn't really matter there

Also, despite what the documentation says, the default for `preference` was actually 0 and not -1. I have tried to correct this and also account for it when converting `preference` to `quality`

youtube_dlc/extractor/zattoo.py

@@ -182,7 +182,7 @@ class ZattooPlatformBaseIE(InfoExtractor):
                 else:
                     assert False
                 for this_format in this_formats:
-                    this_format['preference'] = preference
+                    this_format['quality'] = preference
                 formats.extend(this_formats)
         self._sort_formats(formats)
         return formats