* Instead of launching Tracker/Deskbar directly, we now launch the
Login application.
* This will now start a new session for the selected user (the password
is currently ignored).
* When a user session is started, the launch_daemon forks, and the
child then restarts the LaunchDaemon application in user mode.
* It then registers itself with its parent, in order to resolve user
dependent services.
* Added a user launch file that will cause Tracker, and Deskbar to
start in the new session.
