SS_STATICPUBLISHER_ENABLED - Set in the environment file if static publisher enabled or disabled
SS_STATICPUBLISHER_CACHEDIR - Set the cache directory (if not /cache)
SS_STATICPUBLISHER_DEBUG - modify debug flag.
"This code snippet checks if a page has been modified since it was last displayed. If so, it sends a "304 not modified" header and exits, otherwise the content is rendered." source: http://css-tricks.com/snippets/php/intelligent-php-cache-control/
Adds Last-Modified, Etag (using md5; performance is still good for files under 1MB), and Cache-Control header.
