title: navbarMenu within navbarMenu in Shiny
body: <p>If I use the following UI within Shiny I get roughly the output I want but it isn't actually working as the lowest level navbarMenu displays it's top level label and the arrow to indicate it is expandable but fails to register the sub-items. My guess is because this is designed to be a top-level element only (<strong>navbar</strong>Menu). My question is, is there another element that will perform the desired task of sub-menus? Being unable to group under a menu item would rapidly become visually inefficient.</p>
  
  <pre><code>shinyUI(navbarPage("My Application",
                     tabPanel("Component 1"),
                     tabPanel("Component 2"),
                     navbarMenu("More",
                                tabPanel("Sub-Component A"),
                                tabPanel("Sub-Component B"),
                                navbarMenu("Yet More",
                                           tabPanel("Subpart 1"),
                                           tabPanel("Subpart 2"))
                                )
                     )
  )
  </code></pre>