Only show component selection if there is more than one component configured

[hvangeffen]

Closes #690

Does not fix durban since it still has 2 components:

  "components" : [ {
    "id" : "topologyDisplay",
    "type" : "TopologyDisplay",
    "title" : "Overview",
    "showLeafNodesAsButtons" : false,
    "defaultPath" : {
      "nodeId" : "viewer_saws_1x1"
    }
  }, {
    "id" : "htmlDisplay",
    "type" : "HtmlDisplay",
    "title" : "Terms of use",
    "path" : "terms-of-use",
    "url" : "terms-of-use.html"
  } ]

[wkramer]

I'll check if we have implemented the option to exclude a component from the navigation menu.