Remove the "less" filter name from the base_less.twig

Previously, I was able to use the "lessphp" filter to compile the less files instead of the node based version. I'd prefer to continue using "less.php", which is why I propose to remove the filter name from base_less.twig and add a line to the config file so that ".less" files are automatically matched. This way, both less and lessphp can used by simply modifying the configuration and without changing the templates.