Doco - note in Nginx file to kill a recurring support request.

doc/install/sample-nginx.conf

@@ -66,6 +66,8 @@ server {
   root /var/www/red;
   access_log /var/log/nginx/red.log;
     #Uncomment the following line to include a standard configuration file
+    #Note that the most specific rule wins and your standard configuration
+    #will therefore *add* to this file, but not override it.
   #include standard.conf
   # allow uploads up to 20MB in size
   client_max_body_size 20m;