Merge branch 'feature/independent-php' into 'master'

Ensure the internal PHP scripts work even if system-wide PHP settings are set

Another solution would be to reference the `php.ini` in `./server/lib` from all scripts...but maybe that's a bit of an overkill.

See: http://bugtracker.ispconfig.org/index.php?do=details&task_id=3293&project=3&string=php&type[0]=&sev[0]=&pri[0]=&due[0]=&reported[0]=&cat[0]=&status[0]=open&percent[0]=&opened=&dev=&closed=&duedatefrom=&duedateto=&changedfrom=&changedto=&openedfrom=&openedto=&closedfrom=&closedto=&pagenum=2

See merge request !188