[TYPO3-core] RFC #10600: Clean up sysext usersetup module code

[Steffen Gebert]

Benjamin Mack wrote:
> BT reference: http://bugs.typo3.org/view.php?id=10600
>
> This patch cleans up some of the userSetup module, merging some multiple
> calls in a single functions and simply the logic and checks behind that
> setup module.

REMINDER

I'd like to add an OpenID field to the setup module - but before some 
cleanups/rewrites should be done.

Thanks