Plugin Support

.......... [ZBXNEXT-8330] added default metric support functions for Zabbix agent 2 and plugins

* commit '807451be10624068f914d2c5770e42a1a578f997':
  ..........[ZBXNEXT-8330] fixed metrics with connection parameters with non-empty hardcoded values
  .......... [ZBXNEXT-8330] fixed defaults and added unit test to eval params
  .......... [ZBXNEXT-8330] added default metric support functions for Zabbix agent 2 and plugins