Indicate wether a parent's subtasks is important on the star icon

[raimund-schluessler]

For this purpose a star icon that only shows the outline of the star in the color of the most important subtask could be used.

Such a task should then also be shown in the "Important" collection.

[raimund-schluessler]

For now we won't do this. Let's see if showing all matching subtasks in a collection is already enough.