[validation] add uniquness/scope validation to grading_method_set_item
[locales] grading_method_set_item
[routes] grading method set item
[spec/model] uniquness scope validation for grading method set item
[controller] grading method set items
[factory] grading method set item
[view] show view for grading method set
[view] grading method set items
[spec/req] grading method set item request specs
[fix] typo for new hash syntax