[preview] stats log json v0.5

Rebased https://github.com/inliniac/suricata/pull/1202

Still not happy with the format.

Prscript:
- PR build: https://buildbot.openinfosecfoundation.org/builders/inliniac/builds/67
- PR pcaps: https://buildbot.openinfosecfoundation.org/builders/inliniac-pcap/builds/67