Support SMS alerts

[jace]

Sometimes we need to send a customised SMS alert instead of email alert. Hasmail has almost everything this needs, so there's just a few more tweaks required:

1. When creating a campaign, ask the user to choose if this is email or SMS
2. Recognise a special 'phone' field similar to 'email' and normalize phone numbers (adding country codes if they are missing)
3. In the editing interface, remove the subject line
4. Shorten URLs automatically, per recipient
5. Show a character count that counts the final output size, not the template size
6. Send using multiple SMS gateways similar to how Lastuser and Coaster do it
7. In reports, show delivery stats (pending, delivered, failed) and open stats based on URL opens