[TASK] Support useEmailAddressAsUsername in FeuserEditController

When creating a user there is the useEmailAddressAsUsername option.
But this options isn't yet supported by the FeuserEdit controller.

This patch changes the FeuserEditController so is also respects
this setting.

Change-Id: I6e537c92d252cd8f6ad01ace35f2215f70f93467
Reviewed-on: http://review.typo3.org/33011
Reviewed-by: Sebastian Fischer <typo3@evoweb.de>
Tested-by: Sebastian Fischer <typo3@evoweb.de>