Fix links to notification settings activities.

Additionally, we now show the user a list of "app-like"
things (packages with launchable activities) instead of only
non-system things. This way you can make (some) changes to
system package notifications while not having to page
through reams of random non-app packages.

Bug: 17277023
Change-Id: I920d6b941070efb75a816e6ad38b798b09a83d08