Addition of OpFlex server configuration and message support.

Added configuration of Opflex servers based on changes in
configuration state.

Initial pass at support for the various OpFlex messages
(NB: some of this will change with a later patch that supports
direct serialization/deserialization of messages into the objects,
rather than going through a normalized JsonNode).

Change-Id: I8c5784342656bb8beb48eeec65be547f63d04af0
Signed-off-by: Thomas Bachman <tbachman@yahoo.com>