add grading methods
renamed GradingMethod in lib because of conflict
made grading_method_router static
[helper] load grading method hash
[view] make method input select
[feature/spec] method select in grading method
[model] add validations to grading methods
[factory] change grading method factory
[spec/model] validations for grading methods
Merge pull request #278 from Genshin/grading_method_libs_select

Grading method libs select
Merge remote-tracking branch 'origin/master' into grading_method_libs
updated for moving list to GradingMethod
update specs
add GradingMethod samples, amend grading method forms with Curved box
[views] add missing partials + rename arguemnts to criteria where needed

Conflicts:
	admin/app/views/gaku/admin/grading_methods/_form_fields.html.slim
[js] rename arguments to criteria
[spec/feature] rename arguments to criteria
[js] remove line for placeholder
[locale+view] eg key

Conflicts:
	core/config/locales/en.yml
[migration] make migration more informative/ leave mine