*) report about proxy/fastcgi_store and proxy/fastcgi_cache incompatibility
*) delete useless r->cache->uses
*) proxy_cache_use_stale/fastcgi_cache_use_stale updating
*) inherit proxy_set_header, proxy_hide_header, and fastcgi_hide_header
only if cache settings are similar
*) add response file uniq while loading cold cache on demand