Fixed a regex in ispconfig and apps vhost for nginx: https://www.howtoforge.com/community/threads/possible-bug-in-a-nginx-regex.68948/

- Added check for the apps vhost to find out if the default PHP-FPM pool uses port 9000 or the socket /var/run/php5-fpm.sock.

- Changed FastCGI buffers for ISPConfig nginx vhost because otherwise you get "upstream sent too big header while reading response header from upstream" on OpenSUSE.
- Added 502 error page ("Bad Gateway").
- Added "fastcgi_intercept_errors on;" to nginx vhost template so that ISPConfig's error pages are displayed instead of the default nginx ones.