Utils: Make Layouting a top level namespace

The whole machinery is now almost only layoutbuilder.{h,cpp},
mostly independent of the rest of Utils. Idea is to finish the
separation to make it stand-alone usable also outside creator.

Change-Id: I958aa667d17ae26b21209f22412309c5307a579c
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/libs/utils/aspects.cpp

@@ -30,7 +30,7 @@
 #include <QSpinBox>
 #include <QTextEdit>
 
-using namespace Utils::Layouting;
+using namespace Layouting;
 
 namespace Utils {
 namespace Internal {