Reorganize Service Catalog

Currently each service catalog call handles it's own parsing and
filtering. Modify this so that each function calls back to another
public function ensuring that filtering and parsing is only handled
once.

This allows us to consolidate some helper methods into the base class
and generally clean up.

Change-Id: I15777436af06baea903182f4b3b5913e2890afd1
Extract a base Session object

A wrapper around a number of connection variables. This will be extended
later with principals such as Kerberos authentication and http sessions.

The intent is that this session object will become the basis for all
other client library communications in OpenStack (as keystone wants to
control things like authentication for everybody).

Change-Id: I8ee728c49d554659d7057ebf17d0f8ceea4d7d8e
Part of: blueprint auth-plugins
Merge "Reorganize Service Catalog"