Implement `MeasureNoteOnset14` as `MeasureOnset7` + `NoteOnset7`

[napulen]

This also means implementing MeasureOnset7 and NoteOnset7 in the first place, so

• Implement MeasureOnset7
• Implement NoteOnset7
• Make MeasureNoteOnset14 be a meta-representation that depends on the other two
• The unit tests written for MeasureNoteOnset14 should pass afterwards
• The new input representations should be included in the CLI options for --inputRepresentations

[napulen]

Fixed by #93