Add ip whitelist for client ip restore

1. +++ b/src/EventSubscriber/ClientIpRestore.php
   @@ -107,8 +109,9 @@ class ClientIpRestore implements EventSubscriberInterface {
   +    if ($request_expected_to_bypass_cloudflare || in_array($client_ip, $client_ip_restore_whitelist)) {
   

   in_array() should always have the 3rd param set to TRUE.

2. +++ b/src/Form/SettingsForm.php
   @@ -359,6 +373,7 @@ class SettingsForm extends FormBase implements ContainerInjectionInterface {
   +    $client_ip_restore_whitelist = preg_split('/\r\n|\r|\n/', $form_state->getValue('client_ip_restore_whitelist'));
   

   I'd consider trimming each element of the array and also validating the fact each element is an IP address.

Here's a patch for beta3 - still should address #22.

The patch for 2.0.0-alpha1 also adresses outstanding issues.

Rerolled for 2.0.0-beta1