Enable to add a sidebar in show view

````
show:
  params:
    sidebar:
      'Widget Title':
          parial: AcmeDemoBundle:UserShow:_widget.html.twig
# or
          render: AcmeDemoBundle:Article:recentArticles
# or with params
          render:
            controller:  AcmeDemoBundle:Article:recentArticles
            params:
                max: 3
````