Utils: Add a StringAspect::valueChanged signal

Similar to what BoolAspect already has. Will help with the NimSettings
page.

Change-Id: Id373cd21769c129fb8329d9102ccfd97675e8d24
Reviewed-by: David Schulz <david.schulz@qt.io>

src/libs/utils/aspects.cpp

@@ -820,6 +820,7 @@ void StringAspect::setValue(const QString &val)
     if (BaseAspect::setValueQuietly(QVariant(processedValue))) {
         update();
         emit changed();
+        emit valueChanged(processedValue);
     }
 }
 
@@ -1179,6 +1180,11 @@ void StringAspect::setVolatileValue(const QVariant &val)
     }
 }
 
+void StringAspect::emitChangedValue()
+{
+    emit valueChanged(value());
+}
+
 void StringAspect::update()
 {
     const QString displayedString = d->m_displayFilter ? d->m_displayFilter(value()) : value();