Externalise Email Templates

[RedbackThomson]

Currently we require a commit with new email templates to update the text or look-and-feel of any of our emails. They are sent directly from the web server through SMTP. This limits the analytics we can see on them and has the potential for emails to get lost if not properly delivered.

We hope to move our email templates to SendGrid and use the API to pass any parameters to their service whereby all the analytics can be tracked through them.