The controller test was failing to create any cart_records, due to a strange bug
that prevents active_record objects from being saved or created when they
belong_to :record. This happened with project_affiliated_record as well. The fix
is to change the the belongs_to association to something other than record, and
code the class_name and foreign_key explicitly.

 - cart_record uses a different association name, and adds a validation for record_id
 - cart_record_test tests the validates_presence for record_id
 - test/fixtures/cart_records.yml changed to reflect the new association name
 - ability was changed to make sure admins can create cart_records with any record
 - cart_records_controller_test missspelled assert_equal

ALL TESTS PASS