added code to get events from Zabbix server.

However, this revision fails the following test, because ZABBIX
API emulator hasn't had the corresponding implementation.

  testArmZabbixAPI::test_mainThreadOneProc:             [ERR] <ZabbixAPIEmulator.cc:148> Got exception:
[ERR] <ArmZabbixAPI.cc:301> Failed to get: code: 500: http://localhost:33333/zabbix/api_jsonrpc.php
terminate called after throwing an instance of 'DataStoreException'