Formalization of the extensions to the original Harte syntax used by ChoCo

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Overall there are many chords in ChoCo whose syntax isn't expressed in the original Harte paper, such as hdim, sus2, min11, maj11, 11, min13, maj13, 13, 5, 6, 1/1.

A clear definition of how ChoCo extends the original set of shorthand, along with the degree they are composed of, solves possible ambiguities in the interpretation of chord labels.