Tuskar domain model updates for wireframes

Removed models and DB API calls for data that is no longer being stored
in Tuskar. Added ResourceCategory and Overcloud models, DB API calls,
and unit tests. The controllers that call into the old models will be
removed when I add the controller calls for the new models.

Change-Id: I93492b737bcff1136a276337f6741b88db6214fd
Merge "Tuskar domain model updates for wireframes"