[enh] create blocks for MySQL and PHP command lines which are optionnals.

conf/nginx.conf

@@ -3,7 +3,7 @@ location YNH_WWW_PATH {
   # Path to source
   alias YNH_WWW_ALIAS ;
 
-  # Example PHP configuration
+  # Example PHP configuration (remove if not used)
   index index.php;
 
   # Common parameter to increase upload size limit in conjuction with dedicated php-fpm file
@@ -26,6 +26,7 @@ location YNH_WWW_PATH {
     fastcgi_param PATH_INFO $fastcgi_path_info;
     fastcgi_param SCRIPT_FILENAME $request_filename;
   }
+  # PHP configuration end
 
   # Include SSOWAT user panel.
   include conf.d/yunohost_panel.conf.inc;