YAN-31 add getter for campaignId in PartnerClient.php
YAN-31 add getter for campaignId in PartnerClient.php

AntonShevchuk/yandex-sdk-php,spytz/yandex-php-library,AntonShevchuk/yandex-sdk-php,nixsolutions/yandex-php-library,loginwashere/yandex-php-library,loginwashere/yandex-php-library,spytz/yandex-php-library,nixsolutions/yandex-php-library