Sorting the Project column by project name now

* Including projects in Rate.history_for_user
* Moved the valid sort options to a constant on the RatesController
* Changed the ValidSortOptions to use the Project name for project_id
* Updated admin view to use RatesController::ValidSortOptions instead of a
  duplicated string.

  #1915

app/models/rate.rb

@@ -14,7 +14,8 @@ class Rate < ActiveRecord::Base
   named_scope :history_for_user, lambda { |user, order|
     {
       :conditions => { :user_id => user.id },
-      :order => order
+      :order => order,
+      :include => :project
     }
   }