Add support for select note appearance information

[otsob]

In order to handle note appearance,
as a user,
I want note appearance information that can affect the musical significance of the note to be available.

Acceptance criteria:

• Notehead information is available (note head can signify ghost notes and other playing technique related information)
• Note stem information is available (lack of stem can be significant in some cases)
• Appearance information is read from MusicXML
• Appearance information can be written into MusicXML