Log API v3.0

Changes since https://github.com/inliniac/suricata/pull/772:
- New API: FileLog, so logging file info (not file content)
- Performance improvement for TxLogger
- Port log-file to FileLog API

Prscript:
- PR build: https://buildbot.suricata-ids.org/builders/inliniac/builds/140
- PR pcaps: https://buildbot.suricata-ids.org/builders/inliniac-pcap/builds/60