Fix BlackGui header includes

* Include only what is used
* Use forward declaration when possible
* Sorted includes

refs #598

src/blackgui/components/corestatuscomponent.h

@@ -13,9 +13,13 @@
 #define BLACKGUI_COMPONENTS_CORESTATUSCOMPONENT_H
 
 #include "blackgui/blackguiexport.h"
+
 #include <QFrame>
+#include <QObject>
 #include <QScopedPointer>
 
+class QWidget;
+
 namespace Ui { class CCoreStatusComponent; }
 
 namespace BlackGui