Forward declare as much as possible

src/base/preferences.h

@@ -30,16 +30,17 @@
 #ifndef PREFERENCES_H
 #define PREFERENCES_H
 
-#include <QDateTime>
 #include <QList>
-#include <QNetworkCookie>
-#include <QSize>
 #include <QStringList>
-#include <QTime>
-#include <QVariant>
 
 #include "base/utils/net.h"
 
+class QDateTime;
+class QNetworkCookie;
+class QSize;
+class QTime;
+class QVariant;
+
 enum SchedulerDays
 {
     EVERY_DAY,
@@ -74,8 +75,6 @@ namespace DNS
     };
 }
 
-class SettingsStorage;
-
 class Preferences : public QObject
 {
     Q_OBJECT