Add xForwardedFor Plugin.

This Plugin adds a X-Forwarded-For header field to every request (except it already has one).
It generates a new random IP for every request.
The Plugin can be handy if the target has some kind of "one request per host"-feature

Example:
if(isset($_SERVER['HTTP_X_FORWARDED_FOR'])){
    $ip = explore(',', $_SERVER['HTTP_X_FORWARDED_FOR'])[0];
} else {
    $ip = $_SERVER['REMOTE_ADDR'];
}
Add better discription to xForwardedfor.py
Merge branch 'feature/x_forwarded_for_plugin' into develop