* If the label does not exist yet, it is created.
* The derived buttons are notified if any properties are changed.
* @param[in] properties A Property::Map of key-value pairs of properties to set.
* If the label does not exist yet, it is created.
* The derived buttons are notified if any properties are changed.
* @param[in] properties A Property::Map of key-value pairs of properties to set.