Data Node: make relationship between cross table and data table implicit

Right now we offer an explicit relationship between a Data table and a data_table_node cross table that needs to be added manually when building a view:

  $data[$table->get('name')]['data_table_node_rel'] = array(
        'group' => t('Data node'),
        'title' => "Data table",
        'relationship' => array(
          'help' => t('Relate this data table to data_table_node.'),
          'label' => t('Relate this data table to data_table_node'),
          'base' => 'data_table_node',
          'base field' => 'id',
          'relationship field' => $meta['data_node']['id'],
        ),
      );

We should make this an implicit relationship that does not need to be added manually.

$data['data_table_node']['table']['join'][$table->get('name')] = array(
        'left_field' => $meta['data_table_node']['id'],
        'field' => 'id',
      );