Unify the management interfaces of the SEBA pod parts

The network edge manager (NEM) should take in the various management channels available from the SEBA pod parts including the aggregation Ethernet switch, the OLT hardware, the linux server, and the user interfaces available from the voltha and onos applications.

NEMs should provide an API or a set of APIs available to the operations groups supporting the customers connected by way of the SEBA pod.  These same APIs may be used for northbound systems.

There will be nine user stories associated with this epic.  Most will describe how to handle certain faul conditions, and several will describe requirement for crucial OA&M features including backup and restore, software upgrade, and additional management features.

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