ui: implemented gui abstraction and dummy view

- added abstract class tree for gui elements.
- implemented concrete gui classes that wrap the qt specific content.
- implemented first DummyView which plays nice with the ViewManager.

review id = 12

src/app/qt/QtWidgetWrapper.h

@@ -0,0 +1,27 @@
+#ifndef QT_WIDGET_WRAPPER_H
+#define QT_WIDGET_WRAPPER_H
+
+#include <memory>
+
+#include <QtWidgets/qwidget.h>
+
+#include "gui/WidgetWrapper.h"
+
+class GuiElement;
+
+class QtWidgetWrapper: public WidgetWrapper
+{
+public:
+	static std::shared_ptr<QWidget> getWidgetOfElement(std::shared_ptr<GuiElement> element);
+	static std::shared_ptr<QWidget> getWidgetOfElement(GuiElement* element);
+
+	QtWidgetWrapper(std::shared_ptr<QWidget> widget);
+	virtual ~QtWidgetWrapper();
+
+	std::shared_ptr<QWidget> getWidget(); // not const because returned widget can be changed.
+
+private:
+	std::shared_ptr<QWidget> m_widget;
+};
+
+#endif // QT_WIDGET_WRAPPER_H