title: Adding own action to SonataAdminBundle dropdown menu
body: <p>We use the SonataAdminBundle with our Symfony2 application. When editing an entity I want to add an own action to the dropdown menu which is located in the top right corner, but I have no idea how this works.</p>
  
  <p>I know I can add own routes via <code>configureRoutes(RouteCollection $collection)</code> and how to add batch actions or add own actions behind entities in the list view, but how can I add an own link in the actions dropdown in the edit view?</p>
  
  <p>It is basically just a link like "Show me this entity in the frontend", so no big logic is needed.</p>