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

spec/controllers/rates_controller_spec.rb

@@ -161,6 +161,7 @@ describe RatesController, "as an administrator" do
     before(:each) do
       User.stub!(:find).with(@user.id.to_s).and_return(@user)
       @default_sort = "#{Rate.table_name}.date_in_effect desc"
+      controller.stub!(:sort_clause).and_return(@default_sort)
     end
 
     it "should expose all historic rates for the user as @rates" do