fretboard note labels option

[sugizo]

better to have fretboard note labels option for showing :

• note e.g. A, A#, B, etc
• interval e.g. R, m2, M2, etc
• degree e.g. 1, b2, 2, etc

ref https://en.wikipedia.org/wiki/Interval_(music)#Main_intervals https://en.wikipedia.org/wiki/List_of_musical_scales_and_modes