Hacked some column sorting onto RatesController

* Added SortHelper to RatesController
* Init and updating the sorting (pre 0.8 sort_update)
* RatesController#index will only render the layout on non-xhr requests
* Changed Rate.history_for_user to take an order clause
* Added rate_sort_header_tag and rate_sort_link to the SortHelper in order
  to get the correct parameters for sorting Rates
* Added rate_sort_header_tags to the Rate lists

  #1915

init.rb

@@ -1,6 +1,7 @@
 require 'redmine'
 
 require 'rate_users_helper_patch'
+require 'rate_sort_helper_patch'
 
 Redmine::Plugin.register :redmine_rate do
   name 'Rate Plugin'