Support for deleting images

If an image is in glance and associated with a repo yet was not touched by pulp
during the publish, it will be removed.

There is a failsafe to bail out totally if any images are in pulp that should
have been published and weren't.

The finalize() method could use some refactoring at some point in the future.
It is a little overly verbose right now.
README updates

updates for new functionality
Suggested updates from PR review
spec file for pulp_openstack

This builds the following:

pulp-openstack-admin-extensions
pulp-openstack-plugins
python-pulp-openstack-common

You will need to have python-keystoneclient and python-glanceclient available
when installing.  Both are available from RDO.

This patch requires a tito init after merging. The %changelog will then be populated.