Optimizing slow fetch for addition tasks in quiz editor.
When the quiz editor has to add slides or add questions, the fetches seem to take a long time. This is actually because of the React state update on the whole quiz editor. This branch:
- Delays the state update for synchronized tasks to the end of the pipeline. During synchronous task execution, the quiz editor is disabled anyway...
- It makes sure the internal update function does not update the state if it did not execute any tasks internally.