Update/incident emails#tmp 323

Updates mainly to the format of the emails.  I also did some other minor changes and refactoring along the way including transportforchristchurch.govt.nz -> tfc.govt.nz domain updates, and refactoring the Handlebars helper into its own module.  I wouldn't have necessarily moved this helper out on its own if I didn't first think I was going to add another one, but in the end I ended up not needing a new one so... :sheep: