File structure for uploading zip to be made simpler

[eugenehuangsg]

This thread can serve as a discussion for ideas. Any features approved will spinoff into a new issue for easier organisation.

(1) Provide an interface for instructors to specify regex expression. Give them a few regex expression to select from and specify a corresponding instruction set they can give to their students. System to be able to detect filename that does not fulfill the regex expression and prompt the instructor for verification automatically.

(2) Allow zip of zips files to be uploaded.