Documentation guidelines tweaks

Various small changes that we discussed at the CKAN summit.
Tweak call_action docstring

Make it clear that it skips auth
Fix a couple of broken Sphinx includes
Improve the group test factory

Generate a different name for each test group, and require the user who
will create the group as a param.

This will break some existing tests...
[#1526] Fix some tests broken by commit b117294987
Merge branch 'master' of github.com:ckan/ckan into improved-group-factory
Merge pull request #1489 from ckan/docs-tweaks-from-ckan-summit-winter-2014

Docs tweaks from ckan summit winter 2014
Merge pull request #1526 from ckan/improved-group-factory

Improve the group test factory