Factor parser class out of ChangeNotes

Change-Id: I3f35c452a14713ee69101e85653af623fc5f7b33
Factor parser class out of DraftCommentNotes

Change-Id: Ib7b1eee4ff6aca706dd7b9b301fd6e7882f40431
Extract base class from ChangeNotesTest

Change-Id: I037c2b8d9f80413a313056c13efd47c493b1339a
Move notedb commit message output tests to their own class

Change-Id: Ic739624d713c06d399027bee9d2eb9eb09065dfc
CommitMessageOutputTest: Add helper methods for checking commits

Change-Id: I60f94002b0596e012de66a112e95b91b76f908fa
Add tests for ChangeNotesParser parse failures

Change-Id: I895b75bb502c2057aea0eb24c6b43c721efda7b9
ChangeApi: Implement get/put topic

Change-Id: I8e76f05d52f486b85cb905f7a4bff95966faae79
Merge changes I8e76f05d,I895b75bb,I60f94002,Ic739624d,I037c2b8d, ...

* changes:
  ChangeApi: Implement get/put topic
  Add tests for ChangeNotesParser parse failures
  CommitMessageOutputTest: Add helper methods for checking commits
  Move notedb commit message output tests to their own class
  Extract base class from ChangeNotesTest
  Factor parser class out of DraftCommentNotes
  Factor parser class out of ChangeNotes