Added a helper method to TimeEntry that will encapsulate the rate API for a TimeEntry.

* TimeEntry#cost will return the amount the TimeEntry costs based on:
** logged hours times the assigned rate amount
** logged hours times the effective project rate for the user
** logged hours times the effective default rate for the user
** 0 if the user has no rates at all

  #1924

init.rb

@@ -2,6 +2,7 @@ require 'redmine'
 
 require 'rate_users_helper_patch'
 require 'rate_sort_helper_patch'
+require 'rate_time_entry_patch'
 
 require 'rate_project_hook'