Validate username field on registration

* validate username with regex on registration (bootstrap3 frontent does
  not handle regex correctly. XXX) -> account/forms.py
* small update to registration page title display style
Updated UserProfile admin (account/admin.py)

* displayed one more column 'id'
* added filter function
* changed display style of 'is_approved', 'is_sponsored' and
  'is_checkin': display icons instead of text
Added fields 'sjtu_id' & 'sjtu_initpass' to UserProfile model

* added fields 'sjtu_id' & 'sjtu_initpass' to UserProfile model
* updated 'dump()' and 'dump_fieldnames()' method
* updated 'UserProfileAdmin' to show these fields
* added south migration 0004 for newly added two fields
Updated 'profile.html' and zh_CN locale messages

* updated profile.html to show 'sjtu_id' and 'sjtu_initpass' info
  and show a related alert
* updated zh_CN locale messages