Support for managing the Zabbix Java Gateway.

Hello,

I have added some initial support for managing the Java gateway for those folks that want to query JMX values. It introduces the following attributes

default['zabbix']['server']['java_gateway_enable'] : Default is false
default['zabbix']['server']['java_gateway_pollers'] : Default is 5
default['zabbix']['server']['java_gateway_listen_ip'] : Default is 0.0.0.0 (all interfaces)
default['zabbix']['server']['java_gateway_listen_port'] : Default is 10052 (the project default)

The file layout locations have been loosely inspired by the Debian [Zabbix Java Gateway Package](http://packages.debian.org/sid/zabbix-java-gateway). Some other notes

* The init scripts would be better replaced by systemd/upstart jobs
* If you already have a server running you need to remove /opt/zabbix-X.X.X and /opt/zabbix to trigger a rebuild with the Java gateway enabled
* The yum-epel dependency was also added (removing yum::epel)

This supports the Red Hat and Debian families - it has been tested on CentOS, Red Hat and Debian (not Ubuntu but I'm sure it will work).