HoneyComb support for in-band OAM path tracing

The honeycomb configuration agent for VPP exposes Path Tracing related yang models via netconf or restconf to allow the management of the feature in that VPP instance. There are java plugin APIs needed from VPP that help honeycomb agent configure the VPP instance. The feature can be used to record information like node-id, incoming interface, outgoing interfaces for packets belonging to selected flows to enable the post-processor to gain hop-by-hop information and the path used by the selected flow through the network.

See: https://github.com/CiscoDevNet/iOAM for details.