Added support for SMS fields

`sms_id` in question list is the special id of the group.
`sms_id` in the settings WS is the SMS ID/shortcut of the form
`sms_separator` is the character triggering begining of group ("+" in CC+)
`sms_allow_media` true/false whether to allow binary data (as base64)
`sms_date_format` in settings: strptime-compatible format of date input
`sms_datetime_format` in settings: strptime-compatible format of datetime input
Merge branch 'master' into sms_support
Fixed tests (added sms_id) and added a specific sms one
Changed sms_id in settings to use sms_keyword instead
Merge pull request #88 from modilabs/sms_support

 Added support for SMS fields