Show arrows for counts permanently

[MichHeilig]

In the current version, arrows visualizing the events chronologically are not displayed permanently during the timespan between the first and the last event. Instead, it is shown around the time of every detected event. Hence, the processor cannot be sure that it is the same arrow that has already been shown before.

It would be helpful if the arrow would be displayed permanently during the timespan between the first and the last event.

[arminkollascheck]

The arrows only get shown during the event time window, because it can be confusing for the person who click the count, if there are many counts shown at the same time. Especally at busy intersection or a long travel time between the gates it fast can be a arrow chaos. I see the same problem for the reviewer.

If you select a count, it will show the arrow all the time.