[TYPO3-commerce] Bugfixed version of checkout (stephandling) plus some nice improvements

[Franz Koch]

Hi,

ok, I created some diffs now and uploaded them to bugtracker. As it is 
related to some other bugs in bugtracker I added my diffs to this bug [1]

Hope the diffs are ok. Please test if all works as expected or if I have 
missed to provide some modifications in the diffs.

[1]http://bugs.typo3.org/view.php?id=6222

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Kind regards,
Franz Koch