[view] add set to gradable grading methods
[controller] handle adding set grading methods to gradable grading methods
[spec/features] handle adding set grading methods
[routes] hadnle set grading methods in gradable
[helper] fix can_edit?
[locale]
[helper] fix helper
Merge pull request #281 from Genshin/add_grading_method_set_button_to_gradable

Add grading method set button to gradable