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/controllers/comments_controller.rb

@@ -22,9 +22,6 @@ class CommentsController < ApplicationController
     end
   end
 
-  def search
-  end
-
   def new
     if params[:id]
       quoted_comment = Comment.find(params[:id])