Change configuration saving

* Save initial configuration after all the plugins are done with
  their delayed initialization

* Save configuration when the autosave timer triggers. The disks
  are in use at that time anyway and saving can be turned off
  completely

* Save settings when closing the options page dialog

Change-Id: Idcf9ad61e8f9b94899c580d5a855a883a62f8dc0
Reviewed-by: Majid Khan <mkhan3189@gmail.com>
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/libs/extensionsystem/pluginmanager.h

@@ -135,6 +135,7 @@ signals:
     void aboutToRemoveObject(QObject *obj);
 
     void pluginsChanged();
+    void initializationDone();
 
 public slots:
     void remoteArguments(const QString &serializedArguments);