Integration of a GRPC proxy into the API call chain

To support high availability it is essential that, in the event of a failure, any lost component's tasks can be taken over by another. It is also essential that task distribution among all available components is well balanced.

As new logical devices are added it is essential that they be distributed among all available voltha cores for processing to ensure a well balanced system that is tolerant to failure as well as capable of a speedy recovery.

A proxy supporting GRPC is required that will perform the function of load balancing as well as request distribution equitably across all available voltha cores.