Added the new cookie-based Storage class.

[lex mlist]

Now the session manager has a storage backend cookie-based. It stores the serialized data on the client using a cookie.
You can use it by setting the "sessions" option called "storage" to "cookie".

No files are needed, to get more details on this implementation see the file http://code.google.com/p/spyro/source/browse/trunk/spyro/web/sessions/storage/cookie.py