Use drag-and-drop to reorder grade items instead of numeric sort orders

When reorganizing grade items, Brightspace currently requires instructors to assign numeric sort orders (1, 2, 3, etc.) to move items into a new position. This workflow is cumbersome, particularly in courses with many grade items. Elsewhere in Brightspace (for example, in the Content tool), items can be reordered simply by dragging and dropping them into the desired location.