Fix a bunch of memory leaks on startup->shutdown

include/core/events.h

@@ -187,6 +187,7 @@ public:
     static QString eventGroupToString(Event::Group group);
     static QString eventTypeToString(Event::Type type);
     static Event::Type eventTypeFromString(QString type);
+    static void clearIcons();
     static void setIcons();
 
 // protected attributes

include/project.h

@@ -89,6 +89,8 @@ public:
 
     void clearMapCache();
     void clearTilesetCache();
+    void clearMapLayouts();
+    void clearEventGraphics();
 
     struct DataQualifiers
     {

include/ui/updatepromoter.h

@@ -17,7 +17,7 @@ class UpdatePromoter : public QDialog
 
 public:
     explicit UpdatePromoter(QWidget *parent, NetworkAccessManager *manager);
-    ~UpdatePromoter() {};
+    ~UpdatePromoter();
 
     void checkForUpdates();
     void updatePreferences();