pagination: avoid counting pages outside searches.

Replace this common pattern in controllers:

    @tags = Tag.search(search_params).paginate(params[:page], :limit => params[:limit], :search_count => params[:search])

with this:

    @tags = Tag.paginated_search(params)

`search_count` is used to skip doing a full page count when we're not
doing a search (on the assumption that the number of results will be
high when not constrained by a search). We didn't do this consistently
though. Refactor to do this in every controller.

app/controllers/comments_controller.rb

@@ -89,7 +89,7 @@ private
   end
 
   def index_by_comment
-    @comments = Comment.includes(:creator, :updater).search(search_params).paginate(params[:page], :limit => params[:limit], :search_count => params[:search])
+    @comments = Comment.includes(:creator, :updater).paginated_search(params)
     respond_with(@comments) do |format|
       format.atom do
         @comments = @comments.includes(:post, :creator).load