add support for setting default_type

nginx/templates/config.jinja

@@ -22,7 +22,7 @@ events {
 
 http {
     include /etc/nginx/mime.types;
-    default_type  application/octet-stream;
+    default_type  {{ nginx.get('default_type', 'application/octet-stream') }};
     log_format main '$scheme://$host:$server_port$uri$is_args$args $remote_addr:$remote_user "$request" $request_time $request_length:$bytes_sent $status "$http_referer" "$http_user_agent" "$http_x_forwarded_for"';
     access_log /var/log/nginx/access.fifo main;
     sendfile {{ nginx.get('sendfile', 'on') }};