PackageManager: Restrict system packages to protected storage

Don't allow packages signed with the platform key to be
installed into user (or app) controlled storage

Change-Id: I7390b3bdf5289411f7a335c69635bed9f74bbfb3
Framework: Enable multi-user support for Notification light

Change-Id: I4fb84fdb0c9e1592c2a421011c303a789cde8c8c
Framework:  Fix security exception

Change-Id: I4fa1f55c8209e6890b6cea13b0ed4d781f9f615d