Isolate translation, templating and sending of email as a new drupal module, wmf_communication

Deployment:
* Pause the thank_you module.
* Update source code.
* Enable the wmf_communication module.
* Resume thank_you.

Change-Id: I02da4b157b26d146f663be0345840e4a33f1fb72
Merge "Isolate translation, templating and sending of email as a new drupal module, wmf_communication"