[refs #818] add simple user navigation

app/views/admin/users/_sidebar.html.haml

@@ -1,4 +1,7 @@
 - content_for :sidebar do
+  -if @filter == 'system'
+    .bordered
+      = link_to t("layout.users.list_header"), admin_users_path, :class => 'button'
   .bordered
     - if can? :create, User.new
       = link_to t("layout.users.new"), new_admin_user_path(:system => @filter == 'system'), :class => 'button'
@@ -14,6 +17,6 @@
           %td.width18=radio_button_tag :myradio, 'system', true, {:id => 'users_filter', :class => 'niceRadio', :name => 'filter'}
           %td.width135=t("layout.users.system")
     .both
-  -if params[:action] != 'system'
+  -if @filter != 'system'
     .bordered
       = link_to t("layout.users.system"), system_admin_users_path, :class => 'button'