title: Show values of one2many in tree
body: <p>I have a tree table inside of another tree table. When I'm editing, the nested table is properly shown inside of the cell. But when I just view the values, there are just comma separated ids in the cell (instead of the nested table). How can I display the table in the cell or at least formatted values in the view mode?</p>
  
  <p>Nested table:</p>
  
  <pre><code>&lt;record id="view_mrp_repair_line_item_tree" model="ir.ui.view"&gt;
      &lt;field name="name"&gt;mrp.repair.line.item.tree&lt;/field&gt;
      &lt;field name="model"&gt;mrp.repair.line.item&lt;/field&gt;
      &lt;field name="type"&gt;tree&lt;/field&gt;
      &lt;field name="arch" type="xml"&gt;
          &lt;tree string="Repair line items" editable="bottom"&gt;
              &lt;field name="description" /&gt;
              &lt;field name="price" /&gt;
          &lt;/tree&gt;
      &lt;/field&gt;
  &lt;/record&gt;
  </code></pre>
  
  <p>The parent table:</p>
  
  <pre><code>&lt;field colspan="4" mode="tree" name="operations" nolabel="1" widget="one2many_list"&gt;
      &lt;tree string="Operations" editable="bottom"&gt;
          ...
          &lt;field name="items" context="{'default_repair_line_id':active_id}" widget="one2many_list" /&gt;
      &lt;/tree&gt;
  &lt;/field&gt;
  </code></pre>
  
  <p>Model from nested table:</p>
  
  <pre><code>class mrp_repair_line_item(osv.osv):
      _name = 'mrp.repair.line.item'
  
      _columns = {
          'repair_line_id': fields.many2one('mrp.repair.line', 'Repair Line', required=True),
          'description': fields.char('Description', required=False, size=160),
          'price': fields.float('Price', required=False)
      }
  
  mrp_repair_line_item()
  </code></pre>