Use less relative includes, some of them were wrong

The example now includes them, so we can detect build failures
if they get wrong again

Fixes #140

src/private/widgets/TitleBarWidget_p.h

@@ -12,8 +12,8 @@
 #ifndef KD_TITLEBARWIDGET_P_H
 #define KD_TITLEBARWIDGET_P_H
 
-#include "../../docks_export.h"
-#include "../TitleBar_p.h"
+#include "kddockwidgets/docks_export.h"
+#include "kddockwidgets/private/TitleBar_p.h"
 
 #include <QPainter>
 #include <QToolButton>