core/util: add experimental member macros

An experiment that should reduce boilerplate for properties that just
access a backing value. Code also exists for using it as an interface
for other properties as well, but isn't currently in use.

src/core/types.hpp

@@ -3,8 +3,8 @@
 #include <qdebug.h>
 #include <qnamespace.h>
 #include <qpoint.h>
-#include <qrect.h>
 #include <qqmlintegration.h>
+#include <qrect.h>
 #include <qtmetamacros.h>
 
 class Box {