extend formfields.FormWrapper for a readonly mode

[hugo <gb@…>]

It would be cool if the FormWrapper class would accept an optional parameter readonly. If that parameter is True, the FormWrapper shouldn't generate input statements but just the stuff that would go into the value="" attribute of the input statement. This would allow to use the same template for editing data and for showing data if the logged in user doesn't have the right to edit that dataset - and all this without the need of an additional template or too much changes to the editing template.