Support Printing chords as either letters A-G or Solfege notation

[hpcolus]

Similar to what the songs package offers, an option should be provided to map the "root" names of the chord only for printing the chords in standard letters or the solfege notation (I am not proposing to define chordnames using solfege). The songs package does it with these two commands to map the letters to the Solfege notation. \notenamesin{A}{B}{C}{D}{E}{F}{G} \notenamesout{LA}{SI}{DO}{RE}{MI}{FA}{SOL}

The user might select the preferred output method as follows