Refactory lock screen and screen saver.

src/utilities/Locker.h

@@ -9,12 +9,11 @@ class Locker : public QObject
     Q_OBJECT
 public:
     static Locker* getInstance();
-    void start();
     void stop();
     void setTimer(int aInterval);
-    void setIsEnable(bool aIsEnable);
 
 public slots:
+    void start();
     void refreshTimer();
     void coverScreen();
 private: