New N2VC interface + updated libjuju

This commit introduces the Python3 N2VC module, which acts as a standard
interface to the VCA.

The goal of this is to provide a common way for modules to interface
with the VCA.

- Updated libjuju from 0.6.1 to 0.7.3

Signed-off-by: Adam Israel <adam.israel@canonical.com>
Change-Id: Ide70fb5ae5797eb6486de24653dc09a23f9c009e
diff --git a/modules/libjuju/juju/client/_client2.py b/modules/libjuju/juju/client/_client2.py
index 283e803..6f92a86 100644
--- a/modules/libjuju/juju/client/_client2.py
+++ b/modules/libjuju/juju/client/_client2.py
@@ -1,8 +1,8 @@
 # DO NOT CHANGE THIS FILE! This file is auto-generated by facade.py.
 # Changes will be overwritten/lost when the file is regenerated.
 
-from juju.client.facade import Type, ReturnMapping
 from juju.client._definitions import *
+from juju.client.facade import ReturnMapping, Type
 
 
 class ActionFacade(Type):
@@ -4223,5 +4223,3 @@
 
         reply = await self.rpc(msg)
         return reply
-
-