build: search headers in all source directories

* removed paths in include directives
* changed cmake to provide necessary header search paths
* changed name of version.h to productVersion.h due to name conflict

src/lib_gui/qt/utility/QtDeviceScaledPixmap.cpp

@@ -1,8 +1,8 @@
-#include "qt/utility/QtDeviceScaledPixmap.h"
+#include "QtDeviceScaledPixmap.h"
 
 #include <QApplication>
 
-#include "qt/utility/utilityQt.h"
+#include "utilityQt.h"
 
 qreal QtDeviceScaledPixmap::devicePixelRatio()
 {