[RFE] new variables to handle both ID3v1 and ID3v2


#1

problem: Judging from older threads, there currently is no way to handle both ID3v1 and ID3v2 tags at the same time, which makes it impossible to compare v1 and v2 tags or to copy a specific tag field (like "title") from v1 to v2 or vice versa.

solution: introduce new variables, such as
%title_id3v1%
%title_id3v2%

%album_id3v1%
%album_id3v2%