Implement File3dmNotes for python and javascript

[coditect]

This pull request adds bindings for File3dm.Notes and the File3dmNotes class.

[coditect]

I'm not satisfied with the way the Notes getter on File3dm returns a File3dmNotes that stores a copy of the ONX_Model's ON_3dmNotes object instead of referencing the original. This can lead to unanticipated results in Python and JavaScript when trying to alter a model's notes. For example, the following does not work as one might expect:

myFile = File3dm.Read("/path/to/my/model.3dm")
myFile.Notes.Notes = "These are my new notes"
print(myFile.Notes.Notes) # does not print the new notes

Instead, one has to reassign the modified File3dmNotes back to File3dm.Notes:

theNotes = myFile.Notes
theNotes.Notes = "These are my new notes"
myFile.Notes = theNotes
print(myFile.Notes.Notes) # now it prints the new notes

This situation could be rectified by storing a reference or pointer to ON_3dmNotes inside the File3dmNotes class, but at the expense of added complexity. Since this problem occurs elsewhere in rhino3dm (LineCurve.Line, for example), I wanted to get the input of @fraguada or @sbaer before introducing a new pattern into the library.