Support Grouping/TIT1 tag.

[crocket]

MPD started supporting Grouping/TIT1 tag a while ago upon my request.

According to id3v2.4.0 frames,

TIT1
The 'Content group description' frame is used if the sound belongs to a larger category of sounds/music. For example, classical music is often sorted in different musical sections (e.g. "Piano Concerto", "Weather - Hurricane").

According to Foobar2000:ID3 Tag Mapping - Hydrogenaudio Knowledgebase, TIT1 corresponds to grouping tag in vorbis comment.

I'd like to use Grouping/TIT1 tag for designating the name of movie or game that a song is made for. For example, I want to find movie OST songs by the name of the movie.

I used to use album artist tag for this, but grouping tag is more appropriate.

[adamcik]

If GStreamer supports this then it's probably doable, assuming we add the right field to our models.