!forcepref: Add the smsmode changes from !pref.

Signed-off-by: Martin Stone <martin@d7415.co.uk>
!sms: Fixed erroneous error messages for WhatsApp.

Signed-off-by: Martin Stone <martin@d7415.co.uk>
Switched to my repository for yowsup until the pull request is complete.

Signed-off-by: Martin Stone <martin@d7415.co.uk>