Allow for pure numeric mpaaRating, as apparently generated by kmttg, as
well as iTiVo's tvRating. (Undoes last change, as redundant.) Reported
by "saberman".
Newer FFmpeg treats (at least sometimes) embedded cover art as a video
track, negating the point of the "force_ffmpeg" option, unless we
explicitly disable video with "-vn".
.WTV also needs the config inited. May as well do it for all?