AjaxButton #onSubmit() #onError() intricacies

Overriding AjaxButton's hook #onSubmit() is prone to possible programming errors:

• with JavaScript enabled, #onSubmit() will not be called, leaving the developer without clue that the wrong method was overwritten
• with JavaScript disabled, #onSubmit(ART, Form) will not be called - furthermore if the markup includes type="submit" or no type attribute, #onSubmit() will be called instead.

#onError() and #onError(ART, Form) have identical intricacies.

To make things consistent I propose the following change for Wicket 7.x:

• declare #onSubmit() and #onError() final on AjaxButton
• in #onComponentTag() make sure the <button>-Tag has type="button", so the browser does not submit the form when JavaScript is disabled. For fallack support we have AjaxFallbackButton already.

Any objections or better ideas?