Add write_syslog output plugin

This patch adds an output plugin to send metrics
as CEE-enhanced Syslog log messages by TCP .

The syslog message includes the metrics data in
human readable structured data format and in json
format.

It allows adding additional metedata.

This plugin is based on the write_tsdb plugin.

Signed-off-by: Shirly Radco <sradco@redhat.com>