Moving fieldsets into another region leaves children behind

This issue is a cross-referenced with #1176454: Moving fieldsets into another region leaves children behind. Please read the comment in #10 first before taking up this issue.

In short:
Fields that belong to fieldgroups are not warned they need to move along with their wrapper. A small refactoring in field_group and some additional check in Display Suite can take up the recursive check so that when field groups are moved, everything under it is moved as well.

New code in display suite (patch is coming up with this issue number):

  regionChange: function (region) {
     ...    
     // If a row is handled by field_group module, loop through the children.
     if ($(this.row).hasClass('field-group')) {
       Drupal.fieldUIDisplayOverview.group.prototype.regionChangeFields(region, this, refreshRows);
     }
    
     return refreshRows;
  }

Please checkout field_group from git when trying out.