help, makeapi: specify module topic by name
Specify module topic by name rather than by name and summary. A topic
module of the topic name must exist. Summary is extracted from the
docstring of the topic module.
This changes makes topic handling more generic and consistent between
modules and commands.
https://fedorahosted.org/freeipa/ticket/4739
Reviewed-By: David Kupka <dkupka@redhat.com>