The new effect is based on the mouse click effect and uses the same
rendering code (this could be improved by merging them better).

Unlike mouse click there is no keyboard shortcut needed to activate:
as soon as the effect is loaded all touch points are visualized.

The visualization creates an animated circle for each touch down
position, motion and up position. The ids are tracked and each touch
id gets the same color. The first ten different touch ids get a
different color. As touch ids are stable the first finger will always
have the same color.