Fix coding guidelines incoherences. Code should match PSR1/2 now, and
php-cs is set to check it on each commit.
Also fixed the Git hook to take into account only added, modified,
copied and renamed files (preventing errors when trying to check deleted
files).
Closes#1260.
1) optimization: _xxxChilds: slice whole items array BEFORE converting to output objects
2) fix with special chars in items title.
Some players stops after receiving some special chars.
Don't know which exactly char is wrong, replace all special chars to '-'
Fix: detect if single item is come and convert it to array
2) fix bug with "<?xml..." parse error when php option - short tags - is set
3) upnp broadcast sending page
added button for automatically periodical page refresh for sending broadcast packets without cron, for development purposes
4) Plugins class optimization, method get_plugins
make static cache for optimization when multiple call
