custom data fields seem to have theoretical support for their own lang dirs, but not supported in the field list table

places_to_search_for_lang_strings supports:

'datafield_' => array('mod/data/field'),

but the code that draws up the table of fields (mod/data/field.php) has:

$field->image().' '.get_string($field->type, 'data'),

rather than something like

$field->image().' '.get_string('name', 'datafield_'.$field->type)

Unfortunately since get_string always returns a string it's hard to test first to see if the first place to look returned something before trying the next place (datafield_$type), unless we test for strpos [[ or something which is kind of ick.