Add API to notify web-client about settings changes

Whether this is the final API is still an ongoing discussion.

src/settings/SettingsComponent.h

@@ -66,8 +66,15 @@ public:
   void saveStorage();
   void load();
 
+  // Fired when a section's description is updated.
   Q_SIGNAL void groupUpdate(const QString& section, const QVariant& description);
 
+  // Fired when a subset of a section's values are updated. The values parameter will
+  // contain the names of the changed values as keys, and the new settings values as
+  // map values. Settings which are part of the section, but did not change, are not
+  // part of the map.
+  Q_SIGNAL void sectionValueUpdate(const QString& section, const QVariantMap& values);
+
   void setUserRoleList(const QStringList& userRoles);
 
   // A hack to load a value from the config file at very early init time, before

src/settings/SettingsSection.cpp

@@ -57,7 +57,10 @@ void SettingsSection::setValues(const QVariant& values)
   }
 
   if (updatedValues.size() > 0)
+  {
     emit valuesUpdated(updatedValues);
+    emit SettingsComponent::Get().sectionValueUpdate(m_sectionID, updatedValues);
+  }
 }
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////