Utils/ProjectExplorer: Move re-usabled bits of aspects to Utils

Classes involved are BaseAspect and some derived classes,
LayoutBuilder and VariableChooser.

This is mostly mechanical, with various include/using changes
to make it compile.

Change-Id: I624a457f3555f102e541c4c71e33a9423af32250
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/ios/iosbuildconfiguration.cpp

@@ -47,6 +47,7 @@
 
 using namespace QmakeProjectManager;
 using namespace ProjectExplorer;
+using namespace Utils;
 
 namespace Ios {
 namespace Internal {