Allow change config directory for devstack

Add a new top-level variable CONF_DIR that sets the configuration directory for OpenStack services. Default value is /etc to stay compatible. This allows config files to be moved in to /opt/stack/etc or similar to simplify gathering/removing the config files and allow for the reduction in root requirements.

List server and client API information for python-openstackclient

Implement the first cut at API version detection. May need to use hard-coded API version information to handle the differences in the different services return formats until a common schema is adopted.

API versioning for python-openstackclient

We need to figure out how we are going to handle API versioning to make it uniform for all plugins. Should we, for example, delay creating the CommandManager until we know which version of the APIs we are going to be using? Or is it enough to centralize the API client management?