NETCONF scale improvements

Support management of up to 1 million devices

• maintain persistent connection with all the devices
• all devices of the same type (same yangs)
• small number of yangs per device - one or two
• receive notifications from all these devices
• very hard to support with the current NETCONF plugin

Implementation

• NETCONF plugin to be made available as multiple packages - one for the communicator agent, another for the rest of the NETCONF plugin
• Device communicator agent will handle all the device communication for NETCONF that the device supports.
• ODL-Micro packages for each of these components

Derived from https://docs.google.com/presentation/d/16qOwuMiHQc0aTpmgC8q8tzAOSjdUB7Fom8ZoIj3MTwg/edit#slide=id.g89fa76a8a2_2_23