Implement Preferences::changed() signal.

src/core/preferences.cpp

@@ -165,6 +165,8 @@ void Preferences::save() {
 #else
   delete settings;
 #endif
+
+  emit changed();
 }
 
 const QVariant Preferences::value(const QString &key, const QVariant &defaultValue) const {

src/core/preferences.h

@@ -33,7 +33,6 @@
 #ifndef PREFERENCES_H
 #define PREFERENCES_H
 
-
 #include <QTime>
 #include <QDateTime>
 #include <QList>
@@ -70,6 +69,9 @@ private:
   const QVariant value(const QString &key, const QVariant &defaultValue = QVariant()) const;
   void setValue(const QString &key, const QVariant &value);
 
+signals:
+  void changed();
+
 public slots:
   void save();