Add 'Bounced' status to subscribers [MAILPOET-684]

Fix SubscriberTest->testItHasGroupFilter() making only one of four assertions due to lack of data.
Fix a small issue with Import. Unexpected values for the status field were converted to 'unconfirmed' rather than 'subscribed' due to non-strict comparison in in_array(). This hindered 'bounced' status import as well.

lib/Models/Segment.php

@@ -87,6 +87,10 @@ class Segment extends Model {
         'SUM(CASE subscribers.status WHEN "' . Subscriber::STATUS_UNCONFIRMED . '" THEN 1 ELSE 0 END)',
         Subscriber::STATUS_UNCONFIRMED
       )
+      ->select_expr(
+        'SUM(CASE subscribers.status WHEN "' . Subscriber::STATUS_BOUNCED . '" THEN 1 ELSE 0 END)',
+        Subscriber::STATUS_BOUNCED
+      )
       ->findOne()
       ->asArray();