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/window/QtPathListDialog.h

@@ -1,8 +1,8 @@
 #ifndef QT_PATH_LIST_DIALOG_H
 #define QT_PATH_LIST_DIALOG_H
 
-#include "qt/element/QtPathListBox.h"
-#include "qt/window/QtWindow.h"
+#include "QtPathListBox.h"
+#include "QtWindow.h"
 
 class FilePath;