Add missing api example for incremental backups

* Added Incremental backup test and resulting sample files.
* Fixed the example generator tests to actually fail when api
  changes.
* Added changes since the last example generation was run.
* Added a --fix-examples flag to the example generator to
  automatically correct the sample files.

Change-Id: I7ac355c80b251b0eccd3bd5b8d76d2287c255705
Closes-Bug: #1398119
Merge "Add missing api example for incremental backups"