Port away from most cases of Q_FOREACH to C++11 ranged for loop.

In order to avoid deep copies, Qt containers over which we iterate must be const
The remaining unported cases require qAsConst (Qt 5.7) or std::as_const (C++17)

src/libcalamares/PythonHelper.cpp

@@ -97,7 +97,7 @@ boost::python::list
 variantListToPyList( const QVariantList& variantList )
 {
     bp::list pyList;
-    foreach ( const QVariant& variant, variantList )
+    for ( const QVariant& variant : variantList )
         pyList.append( variantToPyObject( variant ) );
     return pyList;
 }