Add publisher tag
Copy or apply replaygain
Copy lyrics tags

Fix:
    - Use TXXX for arranger, performer (because mid3v2 doesn't recognize
      the TIPL and other tags for this. :(
    - Map lyricist tag
    - Map origin and origintype to TXXX fields
    - Remoeavbe comment tag

Adds:
    - Add option for embedded image art control
    - Enforce TXXX key uniqueness and merge them together with a ;
      character if there are more that one of them.

and also use multiple tags

(untested lol)