Adding an API demo for how to implement printing in an app.

This is a very comprehensive code sample in which:

1. Layout based on the selected print options is performed.
2. Layout work is performed only if print options change would change the content.
3. Layout result is properly reported.
4. Only requested pages are written.
5. Write result is properly reported.
6. Both Layout and write respond to cancellation.
7. Layout and render of views is demonstrated.

Change-Id: I0179b025b286f0a511cb2268da18c729c66874ba
6 files changed