Hook-Method in TabbedPanel to replace a placeholder with an AjaxSubmitLink

[hlemcke]

Based on the solution for #236 (thanks to Sebastien for the quick extension!), I need a hook method in which I can replace some placeholder with an AjaxSubmitLink.

I want to put a link (AjaxSubmitLink) on the tab which sends the form on the panel. The panel gets added after "getLazyPanel()" is invoked. The form for the AjaxSubmitLink does not exist before. So I cannot put the AjaxSubmitLink into method "newTabContainer(...)". I have to put some placeholder there and replace it after "getLazyPanel()" has added the panel with the form to the TabbedPanel.