Added nagios performance data to openvz, qemu vms and storage monitoring.

Option "--perfdata" adds support for graphs with PNP4nagios. Nagios performance data format presented in check_multi style, see http://docs.pnp4nagios.org/pnp-0.6/advanced#check_multi_plugin.

Added option "--html" to replace linebreaks with BR tags.
Merge pull request #5 from dvoryanchikov/master

Added nagios performance data to openvz, qemu vms and storage monitoring...