Utils: Make AspectContainer a QObject

... and add a 'void applied()' signal.

I actually wanted to avoid that, but it seems to be a recurring
pattern of usage to do something on top of plain apply for all
children, like triggering IVersionControl::configurationChanged
in the VCS plugins.

Change-Id: Ib64c3147c6ba30b178237e51a3a377a291c550f2
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/libs/utils/aspects.cpp

@@ -2089,8 +2089,8 @@ public:
 
 } // Internal
 
-AspectContainer::AspectContainer()
-    : d(new Internal::AspectContainerPrivate)
+AspectContainer::AspectContainer(QObject *parent)
+    : QObject(parent), d(new Internal::AspectContainerPrivate)
 {}
 
 /*!
@@ -2192,6 +2192,8 @@ void AspectContainer::apply()
 {
     for (BaseAspect *aspect : qAsConst(d->m_items))
         aspect->apply();
+
+    emit applied();
 }
 
 void AspectContainer::cancel()