Multi-part validation of form by accepting optional parameter for section to validate

Needed multi-part validation for a wizardstyle signup where every page was a part of a form. Had to override 3 methods to accomplish this (mostly copying the old behavior and add an optional argument). Would be great if this optional parameter were added to the core. If you deem the addition acceptable I'd be happy to add some unit tests for it.

Regards
Mattias Brand