When support for prototypeAttrs and automergeAttrs were added, the

intent was for these to be inherited in any subclasses, even if

overridden. However, some logic issues prevented this from working

correctly.
The values from either the parent or subclass's lists were only being

populated if we found the value explicitly set in the subclass. And then

if a subclass set a list, it would likely override the parent's.
We now track any unique values we know we want copied into the subclass,

regardless of whether we copied the corresponding attribute values,

giving us a comprehensive final list.

Unit tests pass.