Show notes in log and commit views about gitiles HOT 2 OPEN

What steps will reproduce the problem?
1. Add a note to a commit
2. Push the notes ref
3. View the commit with the note

What is the expected output? What do you see instead?
The note should be displayed after the commit message. It should also be exposed in
the JSON view. Currently, neither of these is done.

At the least, the note should show up when viewing a specific commit, e.g. 
https://<host>/<repo>/+/<hash>, since this is equivalent to 'git show <hash>'

Even better would be if the note also showed up in the /+log/ view JSON and pretty=full
view.