Plugins class, method get_plugins
make static cache for optimization when multiple call
upnp broadcast sending page
added button for automatically periodical page refresh for sending broadcast packets without cron, for development purposes
fix bug with "<?xml..." parse error when php option - short tags - is set
bug fix: in createDIDL sometimes comes single item, not array. But array is expected. And method crashes.
Fix: detect if single item is come and convert it to array