Drag and drop list reordering for two level lists.
DragAndDropLists is the main widget, and contains numerous options for controlling overall list presentation.
The children of DragAndDropLists are DragAndDropList or another class that inherits from DragAndDropListInterface such as DragAndDropListExpansion. These lists can be reordered at will. Each list contains its own properties, and can be styled separately if the defaults provided to DragAndDropLists should be overridden.
The children of a DragAndDropListInterface are DragAndDropItem. These are the individual elements and can be reordered within their own list and into other lists. If they should not be able to be reordered, they can also be locked individually.