Sort field content alphabetically with external workaround for missing $sort function

[Florian]

@LyricsLover

This would all be much simpler if we had a $sort(x,y,z) script command.

I've added a sort functions with Mp3tag v3.28i, where you can sort a given string that is delimited by a given delimiter, e.g., $sort('c;a;b',';')