StringValidator should set 'minlength' attribute to input and textarea

At the moment StringValidator sets 'maxlength' to input elements.
According to http://www.w3.org/TR/html5/forms.html#the-maxlength-and-minlength-attributes maxlength could be set also to textarea elements.

And there is 'minlength' attribute that could also be set automatically by Wicket.