add "hma" agent for external monitoring host nodes and trigger HA operation.
make original HA trigger obsolete.
add basic monitoring condition primitives.
split json rpc client with zabbix authentication code from drivers/zabbix.rb as helper module.
add monitoring handler to poll status from Zabbix server.
change condition AST design.
add sized array to store fixed size of monitoring result history.
add plain DSLProxy class to avoid method confliction from condtion DSL.
add ntimes continuous status checker for HA monitor DSL.
add And node.
send evacuate_from request after the host node failure.
cleanup unused lines eventually.
Merge branch 'master' into ha-monitor-agent
Merge branch 'master' into ha-monitor-agent

Conflicts:
	dcmgr/lib/dcmgr/node_modules/instance_ha.rb
hma: use common config file loader.
Merge branch 'master' into ha-monitor-agent
Merge pull request #396 from axsh/ha-monitor-agent

HA monitor agent