Update MLClassSelect to allow annotating in batch

Follow-up of #762 (closed): The MLClassSelect component is not capable of handling external updates to its value; it was only designed to allow the user to select something and cause some events to update the value in the parent component, and not to let a parent component update its contents. Since the value is an ML class ID and we want to display a name, the component must be able to retrieve an ML class by ID to display an arbitrary class correctly.