T/nginx optimization

Adds the following:

 * support for multiple php-fpm pools on a single instance
 * support for the same in nginx
 * shorter timeouts between nginx and php-fpm
 * nginx settings like epoll, more worker connections, auto-select of available cores and accept multiple
 * tests for the pool configuration and setup

BIB_ENV is only used here: https://github.com/easybib/www/blob/f8a3ef1497f0f6a3e6138bae442b1d1ec7ba97a0/www/index.php#L55-L70

Maybe we could use this rewrite to remove those hardcoded stack names, and use `::EasyBib::Config.get_stackdata['environment']` instead?