Task queue modifications

Note that this is NOT the same as cancelling out a queue and re-planning it.

Commonly this may be limited to altering and removing elements, adding elements in middle is less common since adding usually places the new item at the end of the queue, however, player may have control over the order the tasks as executed and therefore able to indirectly add new tasks in middle by first creating the new task and then re-ordering it somewhere in middle of the command queue.