Add a receiver to listen for packages being added and removed so the sidebar can reflect those changes.

Change-Id: I336734060f3064fcc3f60d9f48d4a33308a3f20e
Avoid NPE when mExcludedList is null

Patch Set 2:
  Correct logic

Change-Id: Ibaf9ff6996b514284e52a8adcfb5578f9d072eb0