Zabbix

.......... [DEV-1100] added C library linking and log monitoring
* replaced temporary nextcheck calculation with nextcheck calculations from C libraries
* added context parameter to exporter interface
* replaced watcher interface clientid and output parameters with context
* added log plugin providing log, logrt, log.count, logrt.count metrics using C libraries
* added zabbix log related C symbols so linked C libraries will be logging through golang logger