[view] for extracurricular activity, course and class groups enrollments
[controller] for handle Extracurricular, clas group and course enrollment
[routes] for student enrollments
[routes] student enrollments
[model] handle different type of enrollments
[routes] student enrollments
[spec/model] handle different type enrollments
Merge branch 'master' of github.com:Genshin/gaku into enrollmentable

Conflicts:
	frontend/config/routes.rb
	frontend/spec/features/students/class_group_enrollments_spec.rb
[clean] remove comment code
Merge pull request #312 from Genshin/enrollmentable

Enrollmentable