Add an iso repo create command to the admin client.

This is a work in progress.
Fix all the unit tests to reflect the new ISOImporter settings.
Remove a stray print statement.
Add the beginnings of ISO client support for adding distributors when
creating ISO repositories.
Added some unit tests for the create_update.py module in the ISO admin
extensions.
Complete test coverage on pulp_rpm.extension.admin.iso.create_update.
Added a migration to move ISOImporters to the new config names.
Merge branch 'master' into rbarlow-iso-client-create
Added documentation of the ISOImporter setting changes.
Fixed a typo.
Consolidate the ISO Client Authorization CLI option group into the
Publishing group.
Rename a unit test class to be more appropriate.
Call super() in a test class's setUp().
Merge branch 'master' into rbarlow-iso-client-create
Merge pull request #199 from pulp/rbarlow-iso-client-create

Rbarlow iso client create