splitting out (11) from ZBX-2495 ; see images there

as per original issue :

See monitoring-it-service.png and yearly-availability.png. If we click on the green SLA strip marked with a cross in the first picture, and then select period "Yearly", we see the second picture. It shows availability for years 2005-2010, even though we only started running Zabbix in 2010. It should probably be made more intelligent.