Cleanup Qt includes: include the directory name

Cleanup Qt includes: include the directory name
My motivation for this patch is that I don't want to add all the Qt Directory to my include path.
That means I can't use ```#include <QWidget>```.

Or do you mean:
```c++
#if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
#include <QWidget>
// or: #include <QtGui/QWidget>
#else 
#include <QtWidgets/QWidget>
#endif //QT_VERSION
```