Add metadata-only logging feature

[david415]

Some operators may not legally be allowed to use HoneyBadger's full-take logging facilities which is why we need a content stripping logging feature to collect statistics about TCP injection attacks.

Information about the attack that should be logged:

• TCP flow (src port, dst port)
• length of "overlap segments"
• sequence boundaries of "overlap segments"
• date/time of attack
• type of TCP injection attack

[david415]

Obviously to complete this issue you should create another type that implements the AttackLogger interface... but of course your new attack-logger will not record payload data... only metadata... and perhaps an extra CLI option to specify whether or not to record the IP addresses.

Looky here: https://github.com/david415/HoneyBadger/blob/master/attack_logger.go