Enhance Assignment Behavior & Display

Currently, when a task is completed by an assignee, it remains "assigned", so it appears as if it is still due to be done by the assignee in the dashboard table/column view. When a task is complete, it is no longer due and therefore shouldn't have an assignee any longer either. Ideally, the assignee would be cleared from that task. This would allow someone like myself to see only outstanding tasks with assignments, which are the only assignments I would care to track.