Change description of generated link to conform with SMSSync configuration terms

Summary:
Add missing QR code to smssync configuration page

Append SMSSync's Sync URL to step two's description

Test Plan:
 - Go to #messages/settings/smssync
 - See QR code showing
 - See SMSSync's Sync URL

Reviewers: rjmackay, shadowhand

Reviewed By: shadowhand

Maniphest Tasks: T315

Differential Revision: https://phabricator.ushahidi.com/D176