Docs only change: finish documentation of Android Quick Search Box related...

Docs only change: finish documentation of Android Quick Search Box related information in SearchManager.

Includes:
- an overview section on including search suggestions in quick search box
- additional table of searchable metadata attributes related to quick search box
- additional column descriptions that we've added for quick search box.
- description of how to expose your content provider's search suggestions to
the search infrastructure if you have permissions guarding your content provider.