Minor changes in Section 5.3.1

Change the explanation to present a clearer example of a non-active trigger:

From "Note that this does not necessarily represent that one behavior element actively starts another; a traffic light turning green also triggers the cars to go through the intersection." to "Note that this does not necessarily mean that one behavior element actively starts another; in a hypothetical daily process, the “Have Lunch” activity follows (is triggered by) the “Have Breakfast” activity, even though there is no active signal between the two."