Collection of collection which can be called section or category

[Shinichi Okada]

Feature request: Currently it supports only one level of collection. However when a students have many subjects and many topics under each subject, it is desiable to have parent of collection called either section or category.
This can be used in a view to display all the category, such as maths, english, science etc. then it will create a link to a collection of views. This needs an access control as well.