ListValidator should implement MinMaxValidator

If the kernel detects an attribute uses MinMaxValidator it uses the min and max to report min/max or min-length/max-length metadata, with the "-length" option used for model types where that is appropriate. So MinMaxValidator is appropriate for LIST attributes since the data will be reported correctly.

But the primary validator for lists, ListValidator does not implement MinMaxValidator even though it stores and uses a min and max for its validation.