Domaining

Based off #13 
This is a refactor to build our nginx server directives in a more sane fashion.

* Supports passing attributes to php-fpm (aka the application)
* `default_server` has been re-implimented as a separate template, defaulting to country switcher but passing on requests to static assets with the same file paths are the application. This is the basics of 'cookie-free' domains for non-s3 static assets.
* Application domains set to redirect from non-www to www, as per https://github.com/h5bp/server-configs/blob/master/nginx/sites-available/example.com
* Support for our cachebuster including fallback if not in use.
* Turns off nginx `server_token` by default
* Ability to set arbitrary nginx headers and directives.
* turns off php version header by default.

* everything from #13