List of expecting warnings

[lpugin]

This issue lists cases for which the Verovio implementation might be adjusted raise warnings looking at where the specs specify things that SHOULD or SHOULD NOT happen. To be completed.

• Key signature not following the circle of fifths
• Beams in mensural notation
• Consecutive accaciature
• Barlines in neume or mensural notation
• Key signature not after the bar line
• Time signature not after the bar line
• Measure repeats in mensural notation
• Chords with notes not from the lowest to the highest
• Bar lines not a the interval corresponding to the time signature