Added 'syslog_output' support.

I added 'syslog_output' support.  This can help out in a decentralized or dynamic environment, where you might have to use OSSEC in local mode, but want to ship alerts somewhere, without the complexity of agent mode or an OSSEC server.

FYI: OSSEC ships via UDP, so you might want to use rsyslog or nxlog locally to relay this reliably, via TCP. If you want to secure the transport as well, I'd  suggest NXlog's SSL output module.
Since this resource is meant to be server-only, we could just move it to `ossec::server` and omit the extra check. Will help readability too