Put in a "None" or "All of the Above" for Checkboxes, or allow visibility rules

For checkboxes, I can't put in a real "None" because someone can select several options AND none. I would like a "None" or "All of the Above" option. "None" would disappear as soon as something is selected and "All of the Above" would check all of the boxes.

Also, it'd be nice to have my own visibility rules on checkboxes.