Initial support for login with super user admin

'admin' is available for dev use.
developers chould check below session variables when they need to check if the user logged in.
'logged_in' = TRUE/FALSE
'username' (this is the unique and act as user id)
'first_name' 
'role' = 'S' / 'M' / 'U'.
All content updater should have role = 'U', Admin has role 'S', others have role 'M'.