Update VA by checkbox statuses on document ready

Since browsers may cache checkbox statuses, and this probably reflects
customizations chosen by the users, we should make sure VisualArray
notices cached statuses and actually responds to them. (Otherwise, when
the page first loads, the checkboxes may be out of sync with the state
of the VisualArray. This can also be resolved by turning off
autocomplete for the checkboxes, but I thought this way would be
friendlier to users.)