Enrollment page & User Profile page modification

Enrollment page table only has 2 columns now: Name, Status. User can enroll/drop another user by clicking the status. Name is linked to User profile of that user. User Profile page now requires userId in the url, but if a user goes through the navbar's User Profile link, 0 is used as the parameter for 2 reasons:
1. Navbar's dropdown window is genereated before userId is retrieved from server
2. If a user goes to User Profile page through that link, it means the user is accessing his/her own Profile Page so uid is not necessary.