Unable to set name/sort fields for a child datatype

[ajpires]

...if you try, then ODR claims the child datatype has no suitable datafields.

The proximal cause is https://github.com/OpenDataRepository/data-publisher/blame/master/src/ODR/AdminBundle/Controller/DisplaytemplateController.php#L4362 and https://github.com/OpenDataRepository/data-publisher/blame/master/src/ODR/AdminBundle/Controller/DisplaytemplateController.php#L4485 passing in a non-top-level datatype id to DatabaseInfoService::getSpecialDatafields()...function should get refactored to take a datatype object instead of an id. And renamed to getNameSortDatafields() probably.