Initial code drop of netconf protocol implementation

Initial code drop of netconf protocol implementation

This implementation is based on infrastructure provided by the framework artifact
and contains server as well as client side code.

Netconf subsystem structure:
Netconf-api:
Api definition for client and server.

Netconf-impl:
Netconf server implementation. Server handles basic communication
and delegates handling of rpcs to an implementation of netconf-mapping-api.

Netconf-mapping-api:
Api definition for pluggable rpcs handler. Implementations of this api
are plugged dynamically into netconf-impl using OSGi apis.

Config-netconf-connector:
Implementation of netconf-mapping-api that handles netconf rpcs and delegates
requests to configuration subsystem

Netconf-util:
Utility classes used by client and server code.

Netconf-client:
Netconf client implementation.

Netconf-it:
Integration tests for netconf. These tests verify correct cooperation of netconf server,
config-netconf-connector, config subsystem and netconf client.

Config-persister-api:
Api definition for config persister. Config persister is a component that is responsible
for storing configuration snapshots after every change to the configuration via netconf rpcs.
(Pushed to config-subsystem)

Config-persister-impl:
Implementation of config persister that receives notifications from netconf-impl about changes
to the configuration and uses pluggable adapters to store received snapshots.

Config-persister-file-adapter:
Implementation of config persister adapter that stores and restores config snapshots from a file.
(Pushed to config-subsystem)

In order to run netconf in OSGi, some configuration issues had to be resolved
in config-subsystem bundles.

Change-Id: I8e0421c924b0714a4d49962c4bb5ca01ef68ac78
Signed-off-by: Maros Marsalek <mmarsale@cisco.com>