HoneyComb support for in-band OAM Proof-Of-Transit

The honeycomb configuration agent for VPP exposes Proof of transit 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 assumes that the SFC path is set up in the corresponding VPP nodes and the Proof of Transit feature, when enabled via controller like Opendaylight will configure the VPP instances that are part of the SFC path with iOAM configuration that help enable the proof of transit feature.

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