Matroska Song Tagging (continue from Pull Request #225)

[HomerJau]

@TheMinefighter Thanks for doing the Matroska Track fix in #225.

Can we discuss best way to implement 'Songs' in TagLib# for Matroska files?

My interest is using Matroska files for Blu-ray/DVD Concerts (MKV) and Blu-ray Audio albums (MKA for TrueHD/Atmos streams). These are music releases and tagging requires typical audio tags: Song Title, Song Artist, Track (covered with #225), genre, comment at a minimum.

These need to be at a file level (1 file has one song) and at a chapter level (1 files has multiple chapters for each song)

Looking at MP3Tag tagging of MKA files I've found the tag names it uses and can now read/write using MKVPropEdit (MKVtoolnix). But I'm using TagLibSharp for every other music file format. Hence I'd like to look at this here.

The other complexity is although my app is used for tagging (among other things) these Matroska tags need to be read by media players like Kodi. From discussions with Kodi devs, they use TabLib to read tags. So we'd need to get similar 'Matroska Song Tags' into TagLib too.

There doesn't seem to be set tag names for Song tags in the Matroska spec, but there is some used in MP3Tag, currently the ones I use are:
(All TargetTypeValue = 30)
PART_NUMBER = Track (@TheMinefighter pull #225)
ARTIST
TITLE
COMMENT
GENRE

Thoughts?