Object API commands using our REST API layer

* Add object-store API to ClientManager
* Add object-store client
* Add Object API library in openstackclient.object.v1.lib
* Add Object API {container,object} list commands
* Add library tests
* Add command tests

This should complete the Object v1 container and object list commands

Change-Id: Ib1770d45efa8871959826b85faafa1e0bcef0a03