Add points while animation is running

[jwildfire]

Tweaked algorithm to show all points irregardless of date.

• If selected date is before participant's first visit, a small point is shown at the values for the first visit
• if selected date is after participant's last visit, a small point is shown at the value for the last visit.
• if selected date is during participant's enrollment, a normal sized point (scaled to 3rd variable if desired, is shown.