1077506 - [RFE] Support to list details information about one specific pulp repo

https://bugzilla.redhat.com/show_bug.cgi?id=1077506
Now it is possible list information about specific repo in details, summary and specifying different fields.

This commit also contains:
- pep8
- docs
one alternative would be to use the same get_repositories(...) command but use the repo-id as a query param instead of getting the repo directly by id.  The current way works and is prehaps more efficient server side but does have more code to maintain