formatter info is lost when generating the display form

When generating the display mode form the ds field plugin instances do not get the info on which formatter is set. This causes summaries to fail for custom DSFields. We noticed this when using the display_field_copy module as it wouldn't generate the correct summary.
See also issue on that project: #2822398-5: Copied field does not have widget field settings.

This can be fixed in field_ui.inc at line 1117 by adding:

    if (isset($field_settings[$key]['formatter'])) {
      $field['formatter'] = $field_settings[$key]['formatter'];
    }