More configurable thank you generator

Lots of changes:
* No longer generates 2012 messages by default (only 2013)
* It can optionally take the list of required generators
* It can optionally take a list of languages (ignoring all others)
* Moves the placement of some <p> tags to avoid empty elements
* Adds support for the recurring was broken message

Change-Id: Ie383e9c37091b6f09fa25bba9be597bdc8dd9744