[tableview] enhance RelationColRenderer. Closes #2093184 * subvid should only be explicitly specified, or default when main view (vid) is known to support it (eg 'list' / 'csv') * new is_rtype_view boolean flag to ease usage of view based on original entity with a relation name and role, as the 'reledit' view for instance

<div id="ajaxroot">
  <h1>Hello</h1>
</div>