comments: put search form on same page as search results.

* Remove the /comment/search page. Instead put the comment search form
  on the same page as the search results, so you don't have to go back
  and forth to update your search.
* Add an "Edited?" search option, for finding comments that have been edited.
* Add options for sorting by oldest comments and lowest scoring comments.

app/views/static/site_map.html.erb

@@ -83,7 +83,7 @@
         <ul>
           <li><h2>Comments</h2></li>
           <li><%= link_to("Comments", comments_path) %></li>
-          <li><%= link_to("Search", search_comments_path) %></li>
+          <li><%= link_to("Search", comments_path(group_by: "comment")) %></li>
           <li><%= link_to("Votes", comment_votes_path) %></li>
           <li><%= link_to("RSS", comments_path(:atom)) %></li>
           <li><%= link_to_wiki "Help", "help:comments" %></li>