Support a desktop authentication mode.

This uses a single default user in the config database, which is
auto-logged into the app when SERVER_MODE = False. In this mode we
also hide/remove user-related functions in the UI.

web/pgadmin/browser/templates/index.html

@@ -17,18 +17,23 @@
         <li class="dropdown">
           <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-expanded="false">File <span class="caret"></span></a>
           <ul class="dropdown-menu" role="menu">
-            <li><a href="{{ url_for('security.change_password') }}">Change Password</a></li>
             <li><a href="{{ url_for('utils.test') }}">Test URL</a></li>
             <li><a href="{{ url_for('utils.ping') }}">Ping</a></li>
+          </ul>
+        </li>
+      </ul>
+      {% if config.SERVER_MODE %}
+      <ul class="nav navbar-nav navbar-right">
+        <li class="dropdown">
+          <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-expanded="false"><img src="{{ username | gravatar }}" width="18" height="18"> {{ username }} <span class="caret"></span></a>
+          <ul class="dropdown-menu">
+            <li><a href="{{ url_for('security.change_password') }}">Change Password</a></li>
             <li class="divider"></li>
             <li><a href="{{ url_for('security.logout') }}">Logout</a></li>
           </ul>
         </li>
       </ul>
-      <ul class="nav navbar-nav navbar-right">
-        <li><a href="#"><img src="{{ username | gravatar }}" width="18" height="18"> {{ username }}</a></li>
-        </li>
-      </ul>
+      {% endif %}
     </div>
 
   </div>