Fix ShellAppSystem's use of no_focus_window, clean up state handling

First, we were passing an incorrect timestamp to
meta_display_focus_the_no_focus_window - fix that.

The invocation of set_focus_app to the started app there couldn't
really work, because (if the above call had worked) we'd get the
X reply *after* the started app.

What we need to untangle here is the distinction that's now made in
ShellApp between _STATE_STARTING and _STATE_RUNNING.  A nice way to
start doing this is to rebase ShellWindowTracker to only be concerned
with app states.  Concretely, the current "has windows implies
running" logic now lives just inside shell-app.c.

Rename the app-running-changed signal to be app-state-changed.  This
will ultimately be useful so that inside the panel, we can track
the last started app.

https://bugzilla.gnome.org/show_bug.cgi?id=620899

src/shell-app.c

@@ -8,7 +8,7 @@
 #include "shell-enum-types.h"
 #include "display.h"
 #include "st.h"
-#include "shell-window-tracker.h"
+#include "shell-window-tracker-private.h"
 
 #include <string.h>
 
@@ -632,6 +632,8 @@ shell_app_state_transition (ShellApp      *app,
                       state == SHELL_APP_STATE_STARTING));
   app->state = state;
   g_object_notify (G_OBJECT (app), "state");
+
+  _shell_window_tracker_notify_app_state_changed (shell_window_tracker_get_default (), app);
 }
 
 static void