Making setOptions() method actually user configurable and added more curlopts

Until now, the $options array passed to the setOptions() method of modRestCurlClient didn't have any effect as the curlopts were either hardcoded or configured via base modRestClient config params.

With this change it's possible to pass and configure all (and more) curlopts via the $options array that is passed to the request() method like:

```
$options = array('returninfo' => 1, 'curlopt_header' => 1, 'curlopt_nobody' => 1, 'curlopt_filetime' => 1);
```

the above options for example would allow to fetch the last modified timestamp of a remote file without requesting it entirely...

The modifications do NOT alter any previous behavior, as the defaults (if no matching options are passed) are still the same as before, also the additionally added curlopts are not set if not passed explicitely.