Move all order logic to models

- Have a default order for each model
-- The overall default is ID DESC
- Allow for custom orderings
-- When comma-separated IDs are used

app/controllers/users_controller.rb

@@ -22,7 +22,7 @@ class UsersController < ApplicationController
         redirect_to user_path(@user)
       end
     else
-      @users = User.search(params[:search]).order("users.id desc").paginate(params[:page], :limit => params[:limit], :search_count => params[:search])
+      @users = User.search(params[:search]).paginate(params[:page], :limit => params[:limit], :search_count => params[:search])
       respond_with(@users) do |format|
         format.xml do
           render :xml => @users.to_xml(:root => "users")