This reverts commit 2586da8d.
The change was done before the transition from TabbedPane to ListHolder as Action data source, therefore it is no longer necessary.

Might also detect TaskStatus.IN_PROGRESS in a similar fashion using subtask list.

Inspired by `CircleColorPanel`

For better visual clarity.

Instead now, the Task list panels have a border around them + their counter.

Also makes it clear which popup menu utilizes the superiorTaskLisk parameter.

This commit also ultimately removes Utilities.java as there would be no methods left in there, and the *PopupMenu inheritance hierarchy since it has been superseded.