Notifications may now be disabled on a per-package basis.

When a package's ability to post notifications is disabled,
all outstanding notifications from that package are
immediately canceled, and the score of any future
notification from that package is set so low that the
notification manager won't even send it to the status bar.

No UI for this yet, but you can try it out:

  adb shell service call notification 8 s16 $PKG i32 (1|0)

Bug: 5547401

Change-Id: Ieccac5746b40f60debd902a45d1dedbc91dcdc89