Add v16 Notification APIs to NotificationCompat.

As before, we attempt to expose the superset of all
Notification.Builder APIs; where features from the newer
APIs apply to the API level available, we support that
behavior, otherwise we drop it.

This change also has some minor documentation updates that
should be mirrored in the framework.

Bug: 6316809
Change-Id: Ie57625e8bbecae87139f06007b6edd36deee95b1
merge in jb-mr0-release history after reset to jb-dev
Add missing docs to notification style rebuilder functions.

Bug: 6914726
Change-Id: I4b76316dcbfa66b49ec032c57669f33f86b71c2a
merge in jb-mr0-release history after reset to jb-dev
Merge android-4.1.2_r1