Refactor client models in python-barbicanclient

Switching to an OOP approach.
Also did some minor cleanup (removing old Verifications code and some
unused imports).

Change-Id: Ifb443eb0a3ca7bab570d9181b35f6fd5f09e727c
Implements: blueprint client-refactor-models
Merge "Refactor client models in python-barbicanclient"
Work toward Python 3.4 support and testing

Change-Id: Ie06e59518306124e60ab9b741036015f9e977840
Add Containers to python-barbicanclient

Adding Container support to the client and CLI. Also adding Consumer
Registration support at the same time (though not in the CLI).

Change-Id: Id34ac86cfae3f155e97760f14d8cf256722c7d6f
Implements: blueprint client-add-containers
Change object __str__() to use pretty formatting

Use the EntityFormatter framework to generate str() for objects,
and render them using prettytable. Replaces the old manual __str__()
method.

Change-Id: Icf6f37f4a677595f3aaa8d305c2c8cd4676e72fa