Improve commandline error reporting for non-opts

Improve commandline error reporting for non-opts

Before:

```
pdns_server --launch=random --socket-dir=. foo
Fatal: non-option on the command line, perhaps a '--setting=123' statement missed the '='?
```

After:
```
pdns_server --launch=random --socket-dir=. bar
Sep 10 17:24:25 Unable to open /usr/local/etc/pdns.conf
Fatal: non-options (bar) on the command line, perhaps a '--setting=123' statement missed the '='?

pdns_server --launch=random --socket-dir=. bar foo
Sep 10 17:24:25 Unable to open /usr/local/etc/pdns.conf
Fatal: non-options (bar, foo) on the command line, perhaps a '--setting=123' statement missed the '='?
```