commentaries: move search form to /artist_commentaries page.

* Move the commentary search form to the /artist_commentaries page.
* Add Order field for changing the sort order.

app/views/static/site_map.html.erb

@@ -108,7 +108,6 @@
         <li><h2>Artist commentary</h2></li>
         <li><%= link_to_wiki "Help", "help:artist_commentary" %></li>
         <li><%= link_to("Listing", artist_commentaries_path) %></li>
-        <li><%= link_to("Search", search_artist_commentaries_path) %></li>
         <li><%= link_to("Changes", artist_commentary_versions_path) %></li>
       </ul>
     </section>