fix minor issues of  register page and user edit page
minor change of the user new (register page), enable redirect to user home page after register
add if else statement to pages that if no student or other users, show no user information
show username and logout at top-right conner of the page.
Modify the navigation of instructor page. As for now, we don't have any user type, I just check if the user is login. I have issue to change the user type.
Some other minor changes on the style