Add support for a RedHat sysv init script

This patch seperates init scripts into deb LSB and rpm SYSV versions. The sysv version uses nohup to work around the daemonizing problem discussed in https://github.com/elasticsearch/logstash-forwarder/issues/195 (program should daemonized itself)

There are also rpm init scripts out there, that implement systemd support (https://github.com/elasticsearch/logstash-forwarder/pull/175) . So there is the question if redhat <6 native init or 7+ should be supported. Better would be to split the rpm build process into rpms for redhat 5,6 and 7+.

This PR replaces https://github.com/elasticsearch/logstash-forwarder/pull/169 .