Fix poor automatic fretboard calculation

Fix poor automatic fretboard calculation

Improve the automatic fretboard calculation algorithm by changing
the sort order of the notes.

This improvement broke the example on improving automatic fretboards
by specifying a string.  I could not find another example, so I
removed the existing example.  I wanted to leave the text in case
somebody had the problem in the future.

This improvement also fixed the poor diagram for c:9 in the
predefined fretboards section of fretted-strings.itely