Fake cds scripts

Extend repo_generation scripts to be able to generate fake cds structure. Also some refactoryings included. After this change:

* more verbose desription of what is needed to run the script is there
* updated_zoo contains errata with the updated packages, suitable for testing errata detection
* the repo is copied from the pulp at the end of create_repo
* the repo is removed form pulp at the and, if the pulp_id is not specified explicitely (random id is generated)
* the fake_cds.sh script uses the fake_repo definitions and composes the cds structure according to meta.txt (see scp/meta.txt) for details
* srpms are included in the repo as well, for quick changes of the existing repo
* GPG key is copied automatically to the generated repo