!sms: Add an uncaught error when whatsapp is selected as a user's smsmode but a whatsapp login is not specified.
Signed-off-by: Martin Stone <martin@d7415.co.uk>
README.md: Changed to reflect this repository more accurately. Also added details for some extra features that require extra configuration.

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