[Feature request] Add ADF#B tuning

[louis-coding]

add the alternative tuning ADF#B - whether this should be called "european", "canadian" or simply "alternative" is surely debateable

[louis-coding]

I already tried to implement this in a branch of my fork - contributions are more than welcome. It seems to work more or less (chords in song editor are transposed back and forth), but I have not tested it completely...