Change encryption to CTR mode and use better signature

The bakery module seems to add a signature to the cookie based on parts of the user data. I'm not sure I follow why you bother with such as a signature. The hash is created with the same encryption key as the cookie is encrypted with, so if you can encrypt cookies you can also create the hash correctly, so it doesn't add any security if my understanding is correct.

Should the signature just be removed and to save some CPU cycles?