[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/ign.py

@@ -100,7 +100,7 @@ class IGNIE(IGNBaseIE):
             formats.append({
                 'ext': determine_ext(mezzanine_url, 'mp4'),
                 'format_id': 'mezzanine',
-                'preference': 1,
+                'quality': 1,
                 'url': mezzanine_url,
             })