Implement client certification verification
Lumberjack client to support partial acks from server
Merge branch 'features/protocol_improvements_and_server_client_improvements' into features/protocol_client_certificate_verify
Merge branch 'features/protocol_client_certificate_verify' into driskell_merge_pr164
Requires changes to logstash lumberjack input plugin from https://github.com/driskell/logstash