launch_daemon: Basic user session implementation.

* 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.

data/launch/system

@@ -71,13 +71,7 @@ service x-vnd.Haiku-power_daemon {
 	legacy
 }
 
-# The following will be moved into the user launch data
-service x-vnd.Be-TRAK {
-	launch /system/Tracker
-	legacy
-}
-
-service x-vnd.Be-TSKB {
-	launch /system/Deskbar
+job x-vnd.Haiku-Login {
+	launch /system/apps/Login
 	legacy
 }

data/launch/user

@@ -0,0 +1,9 @@
+service x-vnd.Be-TRAK {
+	launch /system/Tracker
+	legacy
+}
+
+service x-vnd.Be-TSKB {
+	launch /system/Deskbar
+	legacy
+}