st2exporter is abandoned

[arm4b]

Suddenly some interesting findings about st2exporter:

• There is [exporter] logging entry in st2.conf
• But /etc/st2/logging.exporter.conf is not shipped and missing
• /opt/stackstorm/st2/bin/st2exporter couldn't be ran because there is no logging conf file
• There are prepared service/init files for deb and rpm in st2-packages repository
• But they aren't shipped
• Ubuntu14.04 service is missing
• CentOS7 service is missing
• There is no entry in st2ctl services for st2exporter

So @Kami @lakshmi-kannan What is that st2exporter thing after all?
Sync-up is needed here to clean-up unneeded config entries or maybe resurrect that forgotten service.

[cognifloyd]

These should clean this up:
#723
StackStorm/st2#5295