Moved entity contents outside navigation.

Previously the entities and navigation are entangled inside a common
DOM structure which limits code reuse. Now they have been moved
into separate structures.

install/ui/index.html

@@ -59,6 +59,7 @@
       </span>
     </div>
     <div id="navigation" class="tabs"></div>
+    <div id="content"></div>
   </div>
 </body>