Notation Reference bug

[Kevin Pye]

In "A.2 Common chord modifiers", the first entry in the table is wrong.

As noted in "2.7.1 Chord mode" under "Extended and altered chords", "as a 
special exception, `c:5` produces a ‘power chord’ only consisting of root and 
fifth". Thus the modifier column should contain only "nothing", the example 
column should just read "C1", and the output column should be updated by 
changing
   \chords{ c1:5 }
   \chordmode{ c1:5}
to
  \chords  { c1 }
  \chordmode { c1 }

As a further illustration of the problem, the second last row shows the "C1:5" 
notation being used correctly.

In addition, the output column for the last two entries should be modified to 
add the chord names:

In the second last row, change
  \chordmode {c1:5 }
to
  \chords { c1:5 }
  \chordmode { c1:5 }

and in the last row, change
  \chordmode {c1:5.8 }
to
  \chords { c1:5.8 }
  \chordmode { c1.:5.8 }

I hope this is useful,

Kevin.