Add a new factory for related items
tests for related_list
Fix pep error
Break down the tests into multiple tests
Merge branch 'master' into related-list-tests
Update factory and related tests

* Delete unnecessary comments from factory.
* Change related factory to accept user parameter.
* Add better docstrings and comments to the related tests.
* Add test to check for invalid sort option.
Merge branch 'master' of github.com:ckan/ckan into related-list-tests
Merge branch 'related-list-tests'