Matroska mapping

[Florian]

@RobertM

I'd thus suggest adopting a similar approach to the mapping of Mp3tag's ALBUM and TITLE fields for MKV files (ALBUM →TITLE T=60, and TITLE →TITLE T=50) would be quite consistent with that two level subtitle approach.

I agree and I've implemented this, along with the changes outlined above, with Mp3tag v3.28f.

Many thanks for your helpful suggestions!