Updates to NR sections 3 and 4 (issue 10782045)

[PhilEHolmes]

Reviewers: ,

Message:
Please review

Description:
There's a fair number of changes here: generally they fall into 2 camps:
1) changing paper size to make the example display properly and 2)
closing up examples with too many line breaks or restated note values.
There are also a few over-long lines with breaks put in them.  Passes
make doc.  Really needs checking with the PDF NR to show the benefits.

Please review this at https://codereview.appspot.com/10782045/

Affected files:
  M Documentation/notation/input.itely
  M Documentation/notation/spacing.itely