zabbix_host: new module for adding or removing hosts on Zabbix

Inspired by the new zabbix_maintenance module in 1.8, I wanted to have a module for adding and removing hosts. I tried to keep the same argument names for this module which are used in zabbix_maintenance. It also uses the same python module. Most of the brain work was already done in zabbix_maintenance.

It can only adding and removing hosts, not updating them for now. But this fits my needs.

Please test it. Feedback is appreciated. I tested it on my shiny new Zabbix 2.2 setup.