simplify verification

Removed unnecessary classes (CookieAuthentication and
UserAuthentication) and added check_login_status() to BaseHandler class
instead. Fixed circular dependancy.
move email/pw/username validiation methods to verification.py in utils
complete code reorganization

Pulled some registration code out of blog and into utils to be used in
other apps, namely the wiki. Added some methods to BaseHandler for a bit
of simplification. Cleaned up some imports following reorganization.