Add const/references to all signal parameters

src/moodbar/moodbarcontroller.h

@@ -36,7 +36,7 @@ class MoodbarController : public QObject {
   void ReloadSettings();
 
  signals:
-  void CurrentMoodbarDataChanged(QByteArray data);
+  void CurrentMoodbarDataChanged(const QByteArray &data);
 
  private slots:
   void CurrentSongChanged(const Song &song);

src/moodbar/moodbarpipeline.h

@@ -47,7 +47,7 @@ class MoodbarPipeline : public QObject {
   void Start();
 
  signals:
-  void Finished(bool success);
+  void Finished(const bool success);
 
  private:
   GstElement *CreateElement(const QString &factory_name);