Provide config to exclude looking up specific IPs

Here's another patch (based on what @MilosR did.
It includes minor naming changes, and some missing methods such as actually saving the form config.

I also moved the check of excluded IPs to query(). However, I do not think this is the right way. But hoping this can give someone a head start to get the feature finalized.

+++ b/src/SmartIp.php
@@ -29,6 +29,14 @@ class SmartIp {
+    if (is_array($excluded_ips) && in_array($data['location']['ipAddress'], $excluded_ips)) {
+      return array();
+    }

In some cases, $data array is not set. For example when IP detection is removed from certain roles.

This will result in a PHP Notice: Undefined variable: data in Drupal\smart_ip\SmartIp::query() (line 36 of smart_ip/src/SmartIp.php)

This needs an isset() check on the $data variable before even querying the $excluded_ips config.