Simplify down to just AuthAction

i.e. with this model, this allows us to map directly onto the default Play way of doing authentication.

@janua, @lindseydew I have had a look through workflow/frontend and I can't find any evidence of them using ```NonAuthAction```. If you think it's worth keeping let me know and we can discuss.
Does not exist yet.  You'll have to publishLocal and make this a snapshot dependency to run this branch.