GUIController: Scene Editor UI...

...initial commit of a scene editor.
GUIController: Completely refactored the project structure
GUIController: SceneDataModel can now read and write data from and to XML file...

SceneDataModel::read() - uses deprecated QtXml module
TODO: Rewrite read to use QXmlStreamReader
SceneDataMode::write() - uses QXmlStreamWriter
GUIController: Scene Editor
GUI Controller: Added functionality to Scene Editor
GUIController: Added QDoubleSpinBox based input cell item to Scene Editor
GUIController: Removed unused field
GUIController: Merged fixes by Ivan Tsantsarov
GUIController: Major refactoring
GUIController: Removed unused for loop in DialogSceneEditor...

...which might have caused a potential bug.