Wizards: let the page use wizard values

For example it will be used to get the
wizard directory to show icons in fields later.

Change-Id: I6a243a67a89e4a0133550a61b870d771147667f1
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/projectexplorer/jsonwizard/jsonfieldpage.cpp

@@ -267,6 +267,16 @@ bool JsonFieldPage::Field::hasSpan()
     return d->m_hasSpan;
 }
 
+QVariant JsonFieldPage::value(const QString &key)
+{
+    QVariant v = property(key.toUtf8());
+    if (v.isValid())
+        return v;
+    auto w = qobject_cast<JsonWizard *>(wizard());
+    QTC_ASSERT(w, return QVariant());
+    return w->value(key);
+}
+
 QWidget *JsonFieldPage::Field::widget() const
 {
     return d->m_widget;

src/plugins/projectexplorer/jsonwizard/jsonfieldpage.h

@@ -125,6 +125,8 @@ public:
 
     Utils::MacroExpander *expander();
 
+    QVariant value(const QString &key);
+
 private:
     static QHash<QString, FieldFactory> m_factories;